The pressure on David Cameron's communications chief Andy Coulson intensified last night after MPs approved an investigation by a parliamentary sleaze watchdog.
The powerful Standards and Privileges Committee will examine claims MPs' mobiles were hacked by News of the World reporters.
All parties backed the fresh probe - sparked by Labour frontbencher Chris Bryant who said he believed many MPs from all sides of the Commons had been targeted.
Ex-royal editor Clive Goodman and private investigator Glenn Mulcaire were jailed for intercepting voicemail messages left for public figures in 2007.
But the row was reignited last week when a former reporter claimed that then NotW editor Mr Coulson was aware such eavesdropping was happening - an allegation he strongly denies.
Bryant told the Commons he was one of the MPs who contacted the Metropolitan Police and was told that he was on a list of those allegedly targeted by Mulcaire.
But he said he suspected that was the "tip of the iceberg" and hacking extended not just to Labour MPs but also to Liberal Democrats and Tories.
He said hacking into MPs' phones was "a contempt of Parliament, a severe breach of parliamentary privilege" which could compromise their right to speak freely, which "stems in essence from the 1689 Bill of Rights".
"I would urge the committee to use all of the powers at its disposal. That includes the power to summon any person it wishes and to require them to attend," he said.
The MPs should investigate whether other newspapers were involved and whether witnesses at the Culture, Media and Sport Committee's inquiry into the matter "lied to the House", he said.
Tory MP John Whittingdale, who chaired that inquiry, backed the fresh inquiry as some of the new claims "appear to contradict some of the evidence that we received".
Earlier, Deputy Prime Minister Nick Clegg urged the police to probe new phone-hacking allegations swirling around Coulson "as quickly and thoroughly as possible".
Labour leadership contender Ed Miliband said Coulson should step aside.
"A week ago I made clear that I believed Andy Coulson had serious questions to answer. There has been no convincing response to the claims that have been made by the New York Times and now we have a parliamentary inquiry," he said.
"Given the cloud that now hangs over him, it seems impossible to believe that Andy Coulson can credibly continue as the director of communications for the British Government."
Liberal Democrat deputy leader Simon Hughes, whose phone was among those hacked and gave evidence in the Mulcaire case, rejected calls for Coulson to step down.
Asked if Cameron had been right to hire the former editor in the circumstances, he told BBC2's Newsnight: "I have not asked him about this but I am sure he both took advice and asked directly the person in question what their involvement was and had the direct assurance, publicly and privately given, that he knew nothing about it.
"If he (Coulson) is clear that he wasn't involved and that is the truth then his position is tenable of course."
Hughes said there were questions about why the police "didn't go further" in their initial investigation.
"In particular it looks like people who might have been victims were not all told."
He also renewed calls for a wider-ranging investigation of the media.
"The really important long-term thing is a Commission into the media so we make sure we don't have the over-powerful media against the democratic state.
"We've got to deal with that, whoever the owners are."
In a statement, the News of the World said: "This matter, which largely relates to alleged behaviour five years ago, has become intensely partisan.
"Amidst a swirl of untethered allegations, there should be no doubt that the News of the World will investigate any allegation of wrongdoing when presented with evidence.
"As we have always made clear, we have a zero-tolerance approach to wrongdoing and will take swift and decisive action if we have proof."
A spokesman for the Standards and Privileges Committee said it was due to meet on Tuesday morning, and would discuss how to take forward the House's instructions.