The abused former resident of a north Wales care home, who said he had been sexually abused by a senior Conservative politician has apologised to peer Lord McAlpine - saying he had mistaken his identity and cleared him of any wrongdoing.
The apology from Steve Messham came as the solicitor for Lord McAlpine, 70, threatened legal action against those in media or on social networks who named him in connection with the scandal.
Messham told the BBC: "After seeing a picture in the past hour of the individual concerned, this [is] not the person I identified by photograph presented to me by the police in the early 1990s, who told me the man in the photograph was Lord McAlpine."
Lord McAlpine, a former Tory treasurer and deputy chairman, has been the subject of intense speculation and innuendo since Messham claimed last week he had been abused by a senior Conservative from the Thatcher era.
But the peer released a strongly-worded statement rejecting any suggestion that he had abused Mr Messham or any other residents of the Bryn Estyn home in Wrexham, North Wales.
In a further statement on Friday night, his representatives said solicitors were preparing writs with a view to taking legal action against "all media who have defamed Lord McAlpine's reputation and published defamatory statements".
Lord McAlpine said he had been defamed by "ill- or uninformed commentators" on the internet and "by innuendo" in the written and broadcast media.
A "substantial number of people" would have "reasonably inferred" that the allegations in the media had referred to him.
"Even though these allegations made of me by implication in the broadcast and print media, and made directly about me on the internet, are wholly false and seriously defamatory, I can no longer expect the broadcast and print media to maintain their policy of defaming me only by innuendo," he said in an earlier statement.
"My name and the allegations are for all practical purposes linked and in the public domain and I cannot rewind the clock.
"I therefore have decided that in order to mitigate, if only to some small extent, the damage to my reputation I must publicly tackle these slurs and set the record straight."
His intervention came as The Guardian became the first newspaper to name him in connection with the allegations this morning in a story suggesting he was the victim of mistaken identity.
The paper quoted Wrexham councillor Keith Gregory, himself a victim of abuse at the Bryn Estyn, saying that he did not believe Lord McAlpine was involved in the scandal.
Lord McAlpine, who now lives in Italy and says he is in poor health, said he was "entirely willing" to meet the chief constable of North Wales, Mark Polin, and National Crime Agency director general Keith Bristow in London as soon as possible "so that they can eliminate me from their inquiries and so that any unwarranted suspicion can be removed from me".
Stuart Newman, the Central Office agent who Lord McAlpine says accompanied him on his sole visit to Wrexham, is now dead.
However, Lord McAlpine's solicitors are trying to contact a senior secretary from CCO at the time "to see if she can remember the precise date I visited".
"I wish to make it clear that I do not suggest that Mr Messham is malicious in making the allegations of sexual abuse about me," Lord McAlpine said.
"He is referring to a terrible period of his life in the 1970s or 1980s and what happened to him will have affected him ever since. If he does think I am the man who abused him all those years ago I can only suggest that he is mistaken and that he has identified the wrong person."
Lord McAlpine's solicitor, Andrew Reid, said the peer had decided to speak out after presenter Philip Schofield tried to pass a list of alleged paedophiles to David Cameron live on ITV1's This Morning programme. The names on the list were briefly caught on camera.
"It becomes a media frenzy and there comes a point at which he has got no choice but to come out and put his case," he told BBC Radio 4's PM programme.
He attacked BBC2's Newsnight programme which last week broadcast Mr Messham's allegations without stating who they referred to.
"They took what I think is the coward's way out. They ran the programme, trailed it, and then told everyone where to go and look for the name. In my view, that is creating the defamation," he said.
"They have done a very, very good job in severely damaging Lord McAlpine's reputation."
The BBC said in a statement to PM: "Newsnight broadcast an investigation into alleged failures in a child abuse inquiry. It worked with the Bureau of Investigative Journalism to give a voice to concerns raised by an abuse victim.
"It was in the public interest to air these. We did not name any public figure for legal reasons. It is now for the inquiries announced by the Home Secretary to dig deeper into Mr Messham's concerns."