British Prime Minister Keir Starmer has apologised to the victims of Jeffrey Epstein, saying he is "sorry for having believed Mandelson's lies and appointed him" British ambassador to Washington.
Mr Starmer insisted that "none of us knew the depth of the darkness" of Peter Mandelson's relationship with the convicted sex offender.
Speaking at an event in East Sussex, Mr Starmer addressed the scandal at the start of a speech as he faces growing pressure from Labour MPs furious about his decision to hand the peer the top diplomatic job.
"It has been publicly known for some time that Mandelson knew Epstein, but none of us knew the depth of the darkness of that relationship," he said.
Mr Starmer said Mr Mandelson was "asked directly" about the nature of his relationship with the paedophile, whether he had stayed with Epstein after his conviction, and whether he had accepted gifts from the financier.
"The information now available makes clear that the answers he gave were lies.
"He portrayed Epstein as someone he barely knew. And when that became clear and it was not true, I sacked him.
"Such deceit is incompatible with public service," Mr Starmer added.
He then apologised to Epstein's victims.
"The victims of Epstein have lived with trauma that most of us can barely comprehend, and they've had to relive it again and again.
"I want to say this: I am sorry, sorry for what was done to you, sorry that so many people with power failed you, sorry for having believed Mandelson's lies and appointed him, and sorry that even now you're forced to watch this story unfold in public once again.
"But I also want to say this: in this country, we will not look away, we will not shrug our shoulders, and we will not allow the powerful to treat justice as optional.
"We will pursue the truth. We will uphold the integrity of public life, and we will do everything within our power and in the interests of justice to ensure accountability is delivered.
"That is what the public expects. That is what the victims deserve, and it is what I will do," Mr Starmer added.
A Labour MP said the political futures of Mr Starmer and his chief of staff Morgan McSweeney are secure.
Housing Secretary Steve Reed said Mr Starmer was not "at fault" because Mr Mandelson "was taken at his word" about his links to the late convicted sex offender Jeffrey Epstein before his appointment as UK ambassador to the US.
"You're only as good as the information you receive," Mr Reed said as he blamed the vetting process for failing to disprove Mr Mandelson's claims his relationship with Epstein "was next to nothing".
Mr Reed said the PM and his right-hand man Mr McSweeney are safe in their jobs, despite backbenchers calling their political judgement into question and demanding Mr McSweeney’s sacking.
Many blame Mr McSweeney, who is from Co Cork, for handing Mr Mandelson the top diplomatic job in Washington despite knowing about his dealings with Epstein continued after his conviction for child sex offences.
One Labour MP, speaking to PA anonymously, said Mr McSweeney "needs to go, he’s a total liability and like Mandelson is only interested in himself".
The MP added: "I think the PM doesn’t have much time left and sadly, he has nobody but himself to blame."
In the face of a mutiny from Labour MPs - led by former deputy prime minister Angela Rayner – the government yesterday backed down and ceded control to the British parliament’s Intelligence and Security Committee to decide what could be released into the public domain.
Another Labour MP told the Press Association: "Morgan is in charge of strategy.
"I think that is what failed yesterday. It's not a one off.
"The Prime Minister was elected by the public and we should focus on making him better."
Paula Barker, Labour deputy chairwoman of the Standards Committee and Privileges Committee, criticised Mr Starmer's "questionable" judgement over the saga but stopped short of calling for him to quit.
On Mr McSweeney, she told the BBC’s Today programme: "There are serious questions to be answered by his (Mr Starmer's) team.
"And certainly, as we know only too well…, when your chief of staff becomes the story, then often it’s time for them to go."
Mr Reed defended the Prime Minister, arguing he was lied to by Mr Mandelson, who he said "conned everybody".
The minister added: "What Mandelson did was he made out that his relationship with Epstein was not only over, but had barely existed in the first place.
"He was taken at his word. There was a vetting process to be gone through that threw up nothing that added further concern to what Mandelson was saying, and so the appointment was made on the basis of his experience as the former EU trade commissioner and former UK business secretary."
Mr Reed also said: "The person at fault here is not the Prime Minister or his team.
"It is Peter Mandelson, who lied, manipulated and deceived everybody."
He also pointed the finger at the vetting procedure which he said "will be looked at".
The release could be delayed because the Metropolitan Police has asked the government not to publish documents that would "undermine" the investigation into Mr Mandelson's passing of confidential government information to Epstein.
Mitchell and Epstein links 'unclear', says Ahern
The nature of the connection between George Mitchell and Jeffrey Epstein is "not clear", former taoiseach Bertie Ahern has said.
There are references to Mr Mitchell in the latest Epstein files, including apparent attempts to arrange a meeting with the former US senator in 2013.
Mr Mitchell has denied all wrongdoing and has expressed regret for ever having known Epstein.
Mr Ahern also described Mr Mandelson as a "tricky guy to deal with".
The former taoiseach worked with Mr Mitchell in the negotiations leading to the Good Friday Agreement, and with Mr Mandelson when he was secretary of state for Northern Ireland.
Queen’s University Belfast has removed a bust of Mr Mitchell, who was chancellor of the institution from 1999 to 2009, from its grounds.
A spokesperson for Mr Mitchell told the BBC on Monday: "Senator Mitchell profoundly regrets ever having known Jeffrey Epstein and condemns, without reservation, the horrific harm Epstein inflicted on so many women."
The spokesperson said Mr Mitchell did not at any time observe, suspect or have any knowledge of Epstein engaging in "illegal or inappropriate conduct with underage women".
In an interview with Newstalk Breakfast, Mr Ahern said he had examined the matter closely as he knew Mr Mitchell "very well" for decades.
He said: "I don't see what he has done - there's a few emails which are unclear whether they were coming from him or they were coming from Epstein, so that's not clear."
He added: "I haven't been across five million documents, so I don't know what's in it but all I can say is that it looks as if Epstein met half the world and he was trying to interact with half the world."
Mr Ahern said it appeared there were a few "back-and-forth" emails between the two men, but added: "God knows what they were about.
"I don't see what George Mitchell is being accused of, it's not clear to me."
He said the nature of redactions in the FBI files meant it was unclear to him if they maintained contact after 2008 - the year in which Epstein was convicted for soliciting a minor.
"If he did, he shouldn't have - but it's not clear," he added.
In the same interview, Mr Ahern said that Mr Mandelson's contacts with Epstein are a "big problem" for the British Prime Minister.
Mr Ahern said: "I think Starmer is in a real difficulty because he knew that he carried on these contacts - that's bad enough I suppose.
"The bigger thing is that he was exchanging information at that level and now they're going to look at what he was at in his time as ambassador.
"It is fairly extraordinary to put him in one of the most senior positions in Washington - the UK ambassador - when you knew his track record.
"He's been fired more times than most people would have in two lifetimes."
Mr Ahern said the "stakes could not be higher" for Mr Starmer due to Cabinet confidentiality.
He added: "Giving away any information to third parties, giving any information outside of the jurisdiction, giving it to somebody with Epstein's record, I mean, it's almost unbelievable."
Mr Ahern reflected on his own experiences with the former Northern Ireland secretary: "Mandelson, to be at my most polite, was a tricky guy to deal with. You really had to check everything and double check everything.
"I dealt with several secretaries of state - most of them straightforward, most of them up front, most of them give you the line fairly straight. But I'm afraid Mandelson wasn't that kind of an individual."
