Former Conservative politician Lord McAlpine has commenced legal action against a long list of organisations and individuals who wrongly linked him to a paedophile ring after coming to a £185,000 settlement with the BBC.
Lawyers representing the peer said action is being prepared against ITV's This Morning and a large number of Twitter users - including the wife of the Commons speaker - who identified him in connection with false sex abuse claims.
It comes after the BBC agreed a libel payout with Lord McAlpine after airing a botched Newsnight investigation into child abuse at a North Wales care home.
The terms of the agreement will be announced in court in a few days' time, according to RMPI LLP, the solicitors to the former Conservative Party treasurer.
The BBC said the settlement was comprehensive and reflects the gravity of the allegations that were wrongly made.
Lord McAlpine said he was "delighted" to have reached a quick and early settlement.
"I have been conscious that any settlement will be paid by the licence fee-payers, and have taken that into account in reaching agreement with the BBC," he added.
"We will now be continuing to seek settlements from other organisations that have published defamatory remarks and individuals who have used Twitter to defame me."
The peer said the damage of the Newsnight report "can't be repaired" and he now has to live with the legacy of suspicion.
Ofcom yesterday revealed it is investigating the broadcast, which led to the resignation of BBC director-general George Entwistle and has further fuelled the crisis which has gripped the corporation since the Jimmy Savile scandal broke.
The regulator has also launched a probe into ITV1's This Morning after presenter Phillip Schofield brandished a list of names of alleged abusers which he had found on the internet and handed it to the Prime Minister during a live interview, asking if he would investigate them. The stunt provoked fury last week, and ITV said that disciplinary action had been taken.
In other developments yesterday a man in his 60s, reported to be DJ Dave Lee Travis, was bailed pending further inquiries after being arrested by detectives investigating the Savile abuse scandal
Lord McAlpine was mistakenly implicated by Newsnight's November 2 broadcast in a paedophile ring that targeted children at a care home in Wrexham.
Although the programme did not name the peer - referring only to a senior Conservative from the Thatcher era - he was quickly identified online.
The peer's solicitor, Andrew Reid, told the World At One programme that action would be taken against "a lot of people" who linked the former politician's name with the unfounded allegations.
He called Schofield's actions "very low" and that the presenter had effectively encouraged viewers to seek out the identity online.
Reid added that a "very long list" of Twitter users had been compiled, including Sally Bercow, the wife of House of Commons Speaker John Bercow, and journalist George Monbiot.
He called on anyone who thought they may have defamed the peer to contact him to reach a settlement, saying this may be the cheapest outcome for them.
The peer's legal team has used specialist companies to track down those who had tweeted or retweeted his name, regardless of whether they had deleted their messages.
In an interview for Radio 4's World At One, Lord McAlpine said the suggestion of being a paedophile was the worst thing of which anyone could be accused, adding that being a figure of public hatred was "terrifying".
Newsnight carried a full, on-air apology for the broadcast a week later.
An official report into the botched investigation by the BBC's Scotland director, Ken MacQuarrie, concluded that Newsnight staff had failed to complete "basic journalistic checks".
MacQuarrie also found there was confusion about who had the ultimate responsibility for "final editorial sign-off", adding that the programme's editorial management structure had been "seriously weakened" as a result of the editor having to step aside over the Savile scandal, and the departure of the deputy editor.
Disciplinary action is being pursued over the incident.
Lord McAlpine said the BBC could have saved "a lot of agonising and money" by simply calling him before the programme went out.