LONDON (CNN) -- The British Broadcasting Corporation has issued a formal apology for broadcasting false claims by a sex abuse victim that a senior political figure of the 1980s had abused him, in the latest in a series of painful missteps by the UK public broadcaster.

The BBC did not name the alleged abuser, but the allegations on its flagship Newsnight program sparked a furor of Internet speculation over who the perpetrator, described as a high-up figure in the government of former Prime Minister Margaret Thatcher, might be.

The broadcaster's apology Friday came hours after Lord McAlpine, who was treasurer of the Conservative Party from the late 1970s until 1990, responded to the online speculation with a statement vehemently denying any involvement.

McAlpine, who now lives in Italy, threatened legal action against those who had wrongly alleged he was the person responsible for the abuse.

The damaging scandal comes in the wake of extensive criticism of the BBC over its handling of sexual abuse allegations against its late TV presenter Jimmy Savile. The broadcaster has set up two inquiries, one into how Savile's abuse went undetected by the BBC over decades, and the second into why an investigation by Newsnight into claims of abuse by Savile was shelved last year, shortly before two tribute programs were broadcast lauding his charity work. The police also face questions over how they handled claims against Savile.

The latest controversy stems from a Newsnight program broadcast November 2 and involves separate allegations made by Steve Messham who was sexually abused in the 1970s and '80s while living in a home in Wrexham, north Wales, where children were cared for by the state.

The scandal picked up such steam that Prime Minister David Cameron was on Thursday presented live on air on Britain's ITV1 channel with a list of names of people who were being speculated about on the Internet.

That action prompted Cameron to warn "that this could turn into a sort of witch hunt, particularly against people who are gay," on the basis of unfounded online rumors.

"If anyone has any information about anyone who's a pedophile, no matter how high up in British society they are, that is what the police are for," he said.

A day later, Messham said in a statement to UK media that he had been wrongly informed by the police that a man he identified as his abuser was the Conservative politician.

"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," he said, according to the BBC.

Messham told the BBC he was "sincerely sorry" over the mistake, saying he wanted justice for everybody who was abused, but that "I certainly don't want the wrong people accused, that is also wrong."

The BBC apology, read out live on air and posted online Friday, said: "We broadcast Mr. Messham's claim but did not identify the individual concerned. Mr. Messham has tonight made a statement that makes clear he wrongly identified his abuser and has apologised.

"We also apologise unreservedly for having broadcast this report."

The BBC also announced an "immediate pause" to investigations by Newsnight.

BBC Director General George Entwistle, who became embroiled in the Savile scandal last month only days after taking the helm at the broadcaster, said on BBC Radio 4's Today program Saturday that the Newsnight claims should not have been broadcast -- but warned against a knee-jerk reaction

"We apologized for it because we should not have put out a film that was so fundamentally wrong. What happened here was completely unacceptable, in my view the film should not have gone out," he said.

A senior BBC editor is to look into the editorial decisions made and disciplinary action may follow, Entwistle said.

But, he added, "The key here is o understand completely what happened before we leap to judgment."

The BBC Trust, which oversees the BBC, said Saturday it was a "deeply troubling episode" and offered its own apology.

"The Trust has impressed upon the Director General the need to get to the bottom of this as a matter of the utmost urgency and will expect an explanation as quickly as possible so that we can ensure that appropriate action is being taken," it said.

In his statement, McAlpine said he had "every sympathy" for Messham and others who were subjected to "abhorrent" sexual abuse while residents of the children's home in Wrexham.

But, he said, he had been to Wrexham only once, in the company of a Conservative Party aide, to visit a local political office, and had never stayed in a hotel there -- the scene of the alleged abuse.

"I did not sexually abuse Mr. Messham or any other residents of the children's home in Wrexham," he said.

"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. 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."

McAlpine threatened legal action against those who have libeled him.

He said he had decided to make the lengthy statement in response to a "media frenzy" around the "wholly false" allegations against him circulating on the Internet.

"My name and the allegations are for all practical purposes linked and in the public domain and I cannot rewind the clock," he said. "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."

Home Secretary Theresa May has ordered an inquiryinto how claims of abuse at a number of children's homes run by Clwyd County Council in north Wales were investigated in the past.

A 1991 police investigation led to eight prosecutions and the conviction of seven former care home workers but questions remained over information gathered by the local authority, May said in a statement Tuesday.

A second inquiry into care home abuse in 1996 named more than 80 people as abusers, many of them care workers and teachers, but "found no evidence of a paedophile ring beyond the care system, which was the basis of the rumours that followed the original police investigation, and indeed one of the allegations that has been made in the last week," the statement said.

In response to the latest furor, May has instructed the head of the National Crime Agency to assess any new claims and review past police investigations into alleged abuse in north Wales care homes.

CNN's Per Nyberg and Alexander Felton contributed to this report.

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