Prime Minister Sir Keir Starmer is facing questions over his appointment of Peter Mandelson as the UK’s ambassador to the US, after he was sacked over his links to the late convicted paedophile Jeffrey Epstein.

Sir Keir fired Mandelson after reviewing emails that showed the Labour peer sent supportive messages to Epstein as he faced charges for sex offences in 2008.

The government said new information about the “depth” of Lord Mandelson’s relationship with Epstein had not been known when he was appointed last year.

The Conservatives are calling for the publication of all vetting material, while some Labour MPs are criticising Sir Keir for appointing Mandelson in the first place.

The prime minister’s spokesman said vetting was handled by government departments and “any suggestion that No 10 was involved is untrue”.

They also said Sir Keir found the emails “reprehensible”.

The Conservatives said the prime minister “needs urgently to come clean” on what he knew when he appointed Lord Mandelson and before Sir Keir backed the Labour peer during Prime Minister’s Questions on Wednesday.

The party demanded the publication of all papers, vetting documents and communications between Downing Street and Lord Mandelson regarding his appointment.

Liberal Democrat leader Sir Ed Davey said the PM “needs to come before Parliament and explain why Lord Mandelson was appointed in the first place, given everything the government knew then”.

There is also discontent within the Labour Party, with some MPs criticising the appointment of Mandelson and the time it took to sack him once new information came to light.

Former deputy leadership hopeful Paula Barker said: “The delay in sacking him has only served to further erode the trust and confidence in our government and politics in the round. We must be better.”

Sir Keir had been dogged with questions over Lord Mandelson’s past friendship with Epstein – which has long been public knowledge – since his appointment as UK ambassador in December.

The BBC has been told the friendship – and the fact it continued after the billionaire was convicted – was part of the PM’s calculation when he was deciding who to send to Washington.

“The Epstein stuff in broad terms was definitely known and discussed in detail before his appointment,” said one source.

In a letter to staff on Thursday, Lord Mandelson said “I deeply regret” the circumstances of his departure from the British embassy in Washington DC.

He said being ambassador had been “the privilege of my life” and he continued “to feel utterly awful about my association with Epstein twenty years ago and the plight of his victims”.

His sacking came after a series of emails were published by the Sun and Bloomberg on Wednesday evening.

In the emails, Lord Mandelson is reported to have told Epstein to “fight for early release” shortly before he was sentenced to 18 months in prison.

Mandelson also told Epstein “I think the world of you”, the day before he began his sentence for soliciting prostitution from a minor in June 2008.

The decision to sack Lord Mandelson was made at a meeting on Thursday morning between the PM and Foreign Secretary Yvette Cooper, the BBC understands.

The BBC has been told the information published on Wednesday evening was not available to those in government when Lord Mandelson was appointed, as they came from what has been described as a “long closed” email address.

Lord Mandelson also did not have access to them and the PM reviewed the material on Wednesday night.

Those in government continue to insist the normal vetting process was followed during the appointment of the ambassador.

Mandelson had generally been seen as doing a good job as ambassador to the US, not least because of his ability to work with the Trump administration.

His sacking comes at an awkward time, just days ahead of a state visit to the UK by US President Donald Trump.

Lord Mandelson would have played a key role, but British diplomat James Roscoe will supervise the visit instead, after taking over as interim ambassador to the US.

A White House official has confirmed to the BBC that President Trump’s state visit to the UK will go ahead next week exactly as planned.

There are no changes as a result of Lord Mandelson’s departure and no comment on him being sacked.

The friendship between Lord Mandelson and Epstein was thrown back into the spotlight on Tuesday, when US lawmakers released a number of documents which included a letter from Lord Mandelson in which he called Epstein his “best pal”.

The alleged “birthday book” given to Epstein in 2003 to celebrate his 50th birthday, also contained messages, cards and photos sent by his friends, including a letter carrying a signature resembling that of President Trump. Trump has denied writing the note.

Epstein was a well-connected financier who was convicted in Florida for soliciting prostitution from a person under the age of 18 in 2008. He died in 2019 while awaiting trial on sex trafficking charges.