The BBC is investigating up to 10 "serious allegations" involving past and present employees, director general George Entwistle said today.
He gave the figure as he faced a hostile grilling from MPs about the broadcaster's handling of claims of sexual abuse by former presenter Jimmy Savile over several decades.
He told the Commons Culture, Media And Sport select committee, when pressed on the scale of current internal investigations: "We are looking at between five and 10 serious allegations relating to activities over the whole period in question, the Savile period."
That included claims of sexual harassment made against people still working at the BBC, he added, but he could not say how many.
Entwistle said Savile's alleged behaviour had been possible only because of a "broader cultural problem" at the BBC.
And there was insufficient evidence yet to say whether or not abuse was "endemic".
But he said it was important to differentiate between complaints of sexual harassment and those of criminal behaviour, such as underage sex.
Opening the hearing, the director general defended the Corporation's handling of the case - including setting up two independent investigations.
"I would accept that there have been times when we have taken longer to do things than in a perfect world I would have liked," he said.
"But I think if you looked at what we have achieved since the scale of the crisis became clear, I think you see we have done much of what we should have done and done it in the right order and with proper respect paid to the right authorities."
Entwistle was also facing criticism over the decision not to broadcast a Newsnight investigation including interviews with Savile's victims last year.
His appearance before the committee came the morning after the BBC's Panorama programme broadcast an investigation into Savile and into the decision to ditch the Newsnight film, at a time when he was head of TV.
Newsnight editor Peter Rippon stepped aside yesterday after the BBC said his explanation of why the show dropped its investigation into Savile was "inaccurate or incomplete".
Entwistle told him Savile's activities were "a very, very grave matter indeed", and said that, when the scale and credibility of the allegations came to light thanks to an ITV investigation, he immediately personally contacted the police.
The scandal had raised questions of trust and reputation in the BBC, he conceded.
He told MPs: "There's no question that what Jimmy Savile did and the way the BBC behaved - the culture and practices of the BBC seemed to allow Jimmy Savile to do what he did - will raise questions of trust for us and reputation for us. There's no question about that.
"It is a gravely serious matter and one cannot look back at it with anything but horror that his activities went on as long as they did undetected.
"Of course, that is a matter of grave regret to me."
Entwistle said the inquiry by Nick Pollard, former head of Sky News, into why the Newsnight investigation into Savile was dropped is expected to report back "in weeks".
He admitted that a factually inaccurate account of the scandal in a blog by Rippon had caused embarrassment.
Entwistle said: "There's no doubt that it is a matter of regret and embarrassment that the version of events recorded in Peter Rippon's blog on October 2 did not turn out to be as accurate as they should have been."
Rippon defended his decision to axe the report in a BBC blog earlier this month but yesterday the corporation issued a correction.
Entwistle told the committee that he had ordered an internal audit of the operation of the BBC's child protection policies and would report its results to the BBC Trust in December.
Asked whether the BBC's existing child protection policies would prevent a future Savile from carrying out similar crimes, Entwistle said: "I believe we have good policies, but I am currently checking them to make sure they are as good as they need to be.
"As to Jimmy Savile, he is dead, so to that extent he has got away with it. But I don't think that can be said to be or seen to be the end of it.
"That's why we are asking Dame Janet Smith to look at this period as thoroughly as she can and understand how that happened, how managerial oversight did fail."
The BBC's head of editorial policy, David Jordan, told the committee: "There's a whole series of measures that are taken now to ensure that children come into the BBC and leave safely.
"The sorts of things that happened, where people were allowed to be taken into the dressing rooms of stars in the BBC, as has been alleged, should not and could not happen today under these arrangements.
"The whole situation has been transformed since the 1960s and 1970s."
Jordan said that, if any allegations emerged which related to people still working for the BBC, the Corporation would ensure that they went to the police and that the individuals involved were denied access to children.
"There hasn't been any need to take that action so far, but every case is scrutinised carefully to ensure that we cannot be in a position where someone who has been accused of any form of sexual abuse is still working in a situation which would allow them to continue to do so," he said.
Entwistle told the committee: "So far as I have been able to tell so far, Savile prosecuted his disgusting activities in a manner that was very successfully and skilfully concealed.
"Experts in paedophile behaviour have pointed out that this is often the case... People build long-range plans to put them in contact with their targets. These things are institutionally, it seems, very difficult to deal with."
The Director-General told MPs he believes the Newsnight investigation into Savile should have continued.
"I came away from Panorama firmly of the view that that investigation, even if, in the judgment of the editor, it wasn't ready for transmission at the point he was looking at it, should have been allowed to continue."
Entwistle said there had been a "breakdown of communication" between Newsnight reports and the editor, Rippon, and he did not feel "confident" he could get an explanation over what happened from within the BBC.
He added: "What became clear to us after the blog was published was that what had happened on Newsnight, there was a significant, it seemed, difference of opinion between the people working on the investigation and the editor, Peter Rippon, who commissioned the investigation.
"That difference of opinion was made clear to me relatively soon after the blog was published the following week.
"Although I would normally absolutely expect to be able to get from the editor of a programme a complete and full picture of what had been going on in that programme, I thought I needed to get to the bottom of why there seemed to be a difference of opinion and there definitely seems to me to have been a difference of opinion.
"There definitely seems to me to have been a breakdown in communication on Newsnight in that regard."
Entwistle was pressed repeatedly by Tory MP Philip Davies about the level of complaints being investigated by the BBC.
Asked if there were active allegations of sexual harassment against existing BBC employees, he said: "Information is being assembled on exactly that subject.
"New allegations are being made and are coming in. What I am looking at is all the existing current allegations."
Existing employees were "included in the numbers" but could not be differentiated, he said, prompting Davies to say he needed to "get a grip" on the organisation.
The BBC was taking "every step we can" to help the police investigate claims that Savile may have been part of a paedophile ring, he told the committee.
He said he would be "worried if there was anything in excess of five" sexual harassment claims made a year against BBC employees - but insisted no level of cases was acceptable.
Conservative MP Therese Coffey branded "chilling" an email sent by Peter Rippon last November that said "our sources so far are just the women" and questioned whether the culture had really changed at the BBC.
"That phrase, on the face of it, isn't in the least defensible, of course," he said. "I do believe the culture has changed since the Seventies and Eighties but I'm not convinced it has changed as much as it should have."
Entwistle told MPs he was bringing in Dinah Rose QC to look at how the BBC handles sexual harassment cases.
He said: "This is something the BBC simply has to get right and I'm not sure we have got it right in every respect at the moment."
'Chain of command'
Entwistle told the committee that he had not personally spoken to any of those involved in preparing the Newsnight film.
He said he felt it was better to operate through the BBC "chain of command", so that he could remain an impartial judge of any subsequent disciplinary case, and had therefore left it to head of news Helen Boaden and deputy director of news Stephen Mitchell to deal directly with the programme.
He said: "I don't believe it would have been appropriate for me to do a detailed examination of what were contended-over documents myself, for fear that I would simply become irrevocably embroiled in that and unable to exercise the authority I am here to exercise as Director-General."
Entwistle said Boaden had spoken to the Newsnight team only briefly during the investigation.
"I understand that Helen's only conversation with Peter (Rippon) in respect of the Newsnight investigation was to remind him that, just because Jimmy Savile was dead, it didn't mean that there could be any skimping in journalistic standards, and that the usual BBC standards would apply," said Entwistle.
Asked whether Rippon might have interpreted that as pressure from above to drop the investigation, the Director-General replied: "I don't regard it as an inappropriate point in any sense to make to an editor. BBC journalistic standards are exactly what Helen is there to support."
Committee member Ben Bradshaw told Entwistle that he appeared to have been "seriously let down by BBC managers".
But Entwistle replied: "I don't think it's right to make that judgment now. The reviews are there to shed light on every aspect of this. Only once the reviews have heard evidence from all the relevant people and made a study of all the documentation will we know exactly what happened."
Entwistle said it was "deeply regrettable" that a blog published under Rippon's name turned out to be inaccurate.
The blog suggested that the Newsnight inquiry was principally into the handling of a Surrey Police investigation into Savile and appeared to indicate that reporters had not turned up significant new information. It was later relied upon by management in setting out the BBC's position,
Entwistle said he was "very disappointed indeed" to learn that it was incorrect.
"What I relied upon is something that in my BBC career I've always been able to rely upon, which is the editor of a programme having a full grip and understanding of an investigation they were in charge of," he said.
"In this case that doesn't appear to have been the case, and that is disappointing."
He said the decision of what material went to air on the BBC was for the editor of an individual programme, and not for him as editor-in-chief. Editors would sometimes refer difficult decisions up to their line manager and divisional director but it would rarely if ever reach the office of the Director-General himself.
"The Director-General has editorial responsibility and accountability for what goes out in his name, but he doesn't have direct editorial control," said Entwistle.
Jordan said that, while preparations had been made for the Newsnight film, it had not actually been commissioned and was therefore unlikely to have been referred up to divisional director level.
Entwistle said: "It seems that Rippon's enthusiasm for the idea was higher at one stage and then became lower, and therefore I wouldn't expect him to be committed to a date or to a referral up."
He said he had since given "considerable thought" to what should be done with journalistic material gathered during an investigation which is not initially broadcast.
"On the basis of what I now know, I am surprised that nothing further happened with it," said Entwistle.
"It seems to me entirely appropriate for an editor to decide - for reasons which he or she in the end has to own - that they are not ready to proceed with an idea, but there was clearly some good journalistic material here.
"Even if there wasn't a prospect of immediate transmission, a continued investigation might have been appropriate.
"One of the questions it's important for the Pollard Review to ask is why was the investigation stopped rather than being allowed to continue, and then there's the question of what should have happened corporately with the information that investigation had discovered."
He said Pollard would look at Rippon's decision to pull the film and the "aftermath" of that decision.
"We have made it clear to Nick Pollard that he is allowed to go wherever his investigation takes him," said Entwistle.
A 'considerate colleague'
Entwistle denied any personal failing, despite being pre-warned that the Newsnight investigation could have an impact on plans to broadcast a television tribute to Savile.
He gave the committee his account of a brief conversation with Boaden at which she alerted him to the potential impact on the scheduled Boxing Day programme.
But he insisted that there was nothing in it that should have given him any reason, as the then head of television, to seek more information.
"I was grateful to her for giving me the heads-up," he said - telling the MPs that it was "relatively rare" for such a conversation to take place.
"But the key message I took away from the conversation was that it wasn't yet clear to Helen whether it was going to stand up or not.
"I left the conversation with an expectation that I would be updated as to whether or not the whole thing was going to happen.
"If someone had said to me 'We are happy with this, this is ready to broadcast', then at that stage I would have expected to engage fully with the consequences."
He thought Boaden was being no more than a "considerate colleague" and did not feel he needed to ask for any further information at that stage, he said.
"I was not relaxed about it but I was critically waiting for the vital piece of information."
That was partly down to his determination to "observe the separate organisation of news and television" and not be seen to be exerting unreasonable editorial pressure, he said.
He complained that had been accused both of intervening to block the Newsnight programme to protect the tribute shows and of not showing enough interest in the Newsnight investigation.
"I was trying to find the right place on that line."
He told the MPs: "I don't believe I did fail, but I believe the system as a whole seems not to have got this right."
Pressed by Whittingdale as to what he thought at the time the nature of the allegations against Savile might be, he said: "I don't remember reflecting on it. This was a busy lunch.
"It wasn't that I didn't want to know. What was in my mind was this determination not to show an undue interest."
Entwistle said he had found no evidence of managerial pressure on Newsnight to drop its investigation.
He told the committee: "I have been able to find no evidence whatsoever in the conversations I have had and in the documents we have now pulled together that any kind of managerial pressure to drop the investigation was applied.
"The decision was made by Peter Rippon on his own account. What was going on in his mind at the time is something we have got to rely on the Pollard Review to interrogate as best it can."
He added: "The consequences of an investigation going out on television or radio are plain to everyone, of course... and I don't believe for a second the BBC would have had any difficulties whatever in re-forming the Christmas schedule in the light of a Newsnight investigation if it had gone ahead.
"We would have been absolutely at pains to do so and would have regarded it as the right thing to do.
"I do think, and I've acknowledged, that we have to address this question of what comes of journalism which doesn't necessarily result in immediate output and yet which contains important information for the Corporation to absorb, either corporately or in terms of a relationship with the police. It's something I need to look at."
'Extraordinary lack of curiosity'
Asked about his conversation at the December 2 lunch with Boaden, Entwistle said: "I assumed that she was preparing me for the possibility that we would need to think about changing the schedule. It was that information I took from the conversation.
"I have no recollection of asking her what it was about."
Whittingdale said he appeared to show "an extraordinary lack of curiosity".
Entwistle replied: "What was informing my judgment - and I think this was emphasised by the fact I came from news and current affairs - was that I absolutely didn't want to do anything that could have been construed as showing an excessive interest.
"I genuinely worry that all sorts of things that people say and do inside the BBC are potentially construable as doing that. Perhaps I was being over-sensitive, but I was being very sensitive to that point."
Conservative committee member Davies said: "It appears that your determination not to show an undue interest applies to everything at the BBC, from today's performance.
"It's not just a lack of curiosity - although it certainly is that - from somebody who has been a journalist, but given that you are putting on these programmes, surely you must have wanted to ask whether or not you can stand something up on Newsnight, is it still appropriate for the BBC to be putting on tribute programmes to this person?"
Entwistle replied: "I didn't ask that question. The possibility that was in my mind was that the investigation wouldn't come to anything. There are all sorts of reasons why an investigation might not come to something.
"I was waiting to hear if I needed to do anything more.
"The thing that was in my mind was that if they had serious allegations that were supportable, it would end in broadcast and I would be told about it and I would act accordingly."
He said that the BBC chain of command, which means that the director general depends on divisional directors' line managers to pass up concerns about programmes or to investigate issues for him, "normally works extremely well".
"There's no question here of anybody trying to turn a blind eye," he said.
Asked about the account initially published in Rippon's blog, Entwistle said: "There's no doubt here in my mind that for us to have published a blog with these inaccurate details in is deeply regrettable, but the key point was for us to establish what those inaccuracies were and publish that account, which is what we've done."
Mntwistle insisted he had not pre-judged the Pollard review despite telling MPs that Rippon made the decision to drop the Newsnight investigation on his own.
"To the best of my knowledge and on the basis of information I have so far, that is what I believe to be the case," he said.
"I have striven today with the committee to answer these questions as fully as I can without endlessly saying 'That's a matter for the review', but, of course, that's a matter for the review."
Entwistle said he would be surprised if the Pollard review could report in "under four or five or six weeks".
Labour's Ben Bradshaw told him it would be "absurd" to "let this drag on" until December.
"Does that not make it all the more important that you get to grip with the facts, that you assemble the facts yourself and act on those facts decisively before this report comes out?" he asked.
Entwistle asked Rippon to 'stand aside'
Entwistle denied that the Panorama programme showed the BBC was "at war" with itself.
"I am editor in chief in the sense that I in the end take responsibility for, and accountability for, all the BBC's journalism," he told the committee.
"That is not the same as expecting every journalistic decision inside the BBC to be referred to me.
"I regard the independent right of the editor of Panorama to decide what he should investigate, even when that concerns the corporate affairs of the BBC, to be inalienable."
He declined to be drawn on Rippon's future when he was asked by Labour former culture secretary Bradshaw to rule out any deal for him to "go quietly" in return for the BBC "not completely trashing his account of events".
Entwistle said: "Peter Rippon will take part in the Pollard review. The findings will be made available first to the BBC Executive before they are then passed to the Trust.
"The BBC Executive's task will be to make an immediate decision about whether any disciplinary consequences should flow from the Pollard review.
"I don't think it would be fair to say anything else that would prejudice any of that process."
Entwistle said the reporter responsible for the Newsnight investigation, Liz McKean, and producer Meirion Jones continued to work with Rippon on the programme. McKean is still working on Newsnight, while Jones is now attached to Panorama, he said.
And he said he personally asked Rippon to "stand aside" from the programme because of the inaccuracies in his blog.
"I have asked Peter Rippon to stand aside because of my disappointment in the nature of the blog and the inaccuracies in the blog," said Entwistle.
"What he is going to do now he has stepped aside is concentrate on preparing for the Pollard Review. But can I be clear, he hasn't stepped aside to prepare. I have got, in all fairness, to allow him to go into the Pollard Review with the best possible chance of being able to make his case and be vindicated about his case.
"That's the only fair thing to do in respect of the Pollard Review. I don't want to say anything else that might prejudice his prospects in that regard."
Labour committee member Paul Farrelly said the key unresolved question with regard to Newsnight was why Rippon had "a sudden change of mind (and)... who sat on him and helped to change his mind? Was it the director of news?"
Entwistle replied: "Is it not possible that he changed his mind? From what I can see, he became more and more seized of the importance of the Surrey Police investigation and the reasons for the police not proceeding and the CPS not proceeding on the basis of the information they had.
"He became convinced that without that, he didn't have what he needed to make the story.
"As far as I am concerned, it doesn't need any external agency for Peter Rippon to change his mind."
Entwistle said he would find it hard to say how long his December 2 conversation with Boaden lasted.
"I can't pretend to recall precisely what she said to me," he said. "But it was words to the effect 'Newsnight are looking at Jimmy Savile. When it is clear if it is going to go ahead or not and whether it stands up, it may have implications for your schedule'.
"I have no recollection of asking any further questions. I don't recall anything else being said to me afterwards."
Entwistle said that Boaden did not specifically say to him that it was the plans for tributes to Savile that might be disrupted, but he assumed that this was what she was referring to.
Entwistle said he made the BBC Trust and its chairman Lord Patten aware of the allegations against Savile after his initial contact with police on October 2 this year.
"I think the BBC Trust should be kept apprised of anything important to the organisation, insofar as the organisation knows what it is and is dealing with it as it should," said the director general.
"I don't think the BBC Trust should have been told about a Newsnight investigation in its early stages. If the significance of what Newsnight had found had been recognised and properly dealt with by the organisation as a whole, it may well have been that the Trust would have been told about it.
"I think it should be told when allegations are substantiated. There's got to be a difference between allegations which are being investigated and allegations which are substantiated."
'A very grave and serious issue'
Entwistle left through a scrum of reporters and cameras but refused to say much, beyond asking that the BBC's internal inquiries be allowed to do their work.
He said: "I've just taken two hours of questions from the Culture and Media Select Committee so you'll understand I'm not going to take any more.
"What I do want to say is what needs to happen next is the two independent reviews that have been set up must be given their chance to do their work. That's what I hope you'll all help us do."
Entwistle had insisted to the committee that the BBC pursued the allegations against Savile with the same "vigour" as it would have done with a similar story about a celebrity linked to a rival network.
"For all the many years that people say they heard rumours and allegations, no newspaper landed an investigation into Jimmy Savile that I am aware of, and no other broadcaster did," the director general told the committee.
"So it is not like there was a period of immense vigour from other people and not from the BBC.
"We now understand he was a very successful and skilful sexual predator who covered his tracks.
"The Panorama programme last night interviewed a number of people who said they worked closely with him and saw nothing to give rise to suspicions, and then of course it had the account of the group of people around Radio 1 who did ask him questions but were reassured by what he told them that the thing they were asking him about was not true."
Entwistle said the BBC management acted differently when the scale of the Savile allegations came to light compared to the accusations of inaccuracy in its report of weapons inspector David Kelly's concerns about the Government's dossier on Iraq in 2003.
"One of the key distinctions between what happened over the Kelly affair and what happened in this case is that I have set up an independent inquiry within a matter of day of the scale of the problem becoming clear," he said. "There was no such process in the case of what happened with David Kelly."
Asked whether Rippon might have been acting with too much risk-aversion when he decided to pull the Savile story, Entwistle said: "It is important to recognise during a time like this that 95%-plus of what the BBC does is still going on.
"We have a very, very grave and serious issue here that has to be dealt with, but the imperative for the organisation to be creatively and journalistically adventurous is incredibly strong.
"It is something I intend to devote time and focus to, trying to eliminate creative risk-aversion and journalistic risk-aversion if I find it and ensuring we are absolutely as bold as we should be."