The United Kingdom’s ambassador to the United States, Peter Mandelson, told Jeffrey Epstein to “fight for early release”, according to leaked emails.

He also allegedly wrote “Your friends stay with you and love you” when the disgraced financier was facing charges of procuring a child for prostitution.

The emails, first published by the Sun after circulating in Washington DC, will put further pressure on Mr Mandelson after he admitted on Tuesday that more “very embarrassing” details of his friendship with Epstein were likely to emerge but insisted he had never seen any “wrongdoing”.

In an email from June 2008, which was not disputed by his spokesperson, Mr Mandelson wrote to Epstein: “I think the world of you and I feel hopeless and furious about what has happened.

“I can still barely understand it. It just could not happen in Britain. You have to be incredibly resilient, fight for early release and be philosophical about it as much as you can.”

It continued: “Everything can be turned into an opportunity and that you will come through it and be stronger for it.”

An extract from the 50th birthday album compiled in 2003 for Jeffrey Epstein, contributed by Peter Mandelson, which shows an image of the two together along with the message 'But, wherever he is in the world, he remains my best pal!' Photograph: US Committee on Oversight and Government Reform/PA WireAn extract from the 50th birthday album compiled in 2003 for Jeffrey Epstein, contributed by Peter Mandelson, which shows an image of the two together along with the message ‘But, wherever he is in the world, he remains my best pal!’ Photograph: US Committee on Oversight and Government Reform/PA Wire

The friendship between the two men has come back into the spotlight after Democratic members of the US House oversight committee released Epstein’s 50th “birthday book”, in which Mr Mandelson called him “my best pal” in a handwritten note.

Donald Trump, the US president, is also under scrutiny over his relationship with Epstein, having also allegedly contributed to his 50th birthday book – although he has denied the authenticity of the letter and dismissed it as a fake.

The Telegraph reported that when Mr Mandelson was UK business secretary in 2010, and after the financier’s release from jail, he allowed Epstein to help broker a deal for JP Morgan to buy part of a commodities firm from the UK government-owned RBS bank.

Trump calls release of suggestive note to sex offender Jeffrey Epstein a ‘dead issue’Opens in new window ]

Mr Mandelson served as secretary of state for Northern Ireland from 1999 to 2001.

No 10 stood firmly behind Mr Mandelson on Wednesday, saying he had been fully security-checked before taking up the role and was the right person for the job.

However, the new emails are likely to raise further questions about whether the prime minister knew the full extent of Mr Mandelson’s support for Epstein when he appointed him US ambassador earlier this year.

The Conservatives have called for Mr Mandelson to be sacked and the Liberal Democrats have demanded an investigation by the civil service commissioner into whether the diplomatic service code has been broken.

Kemi Badenoch, the Conservative leader, said they were “sickening revelations” and that Mr Mandelson’s position is untenable.

A number of Labour MPs are privately furious about prime minister Keir Starmer’s judgment in appointing Mr Mandelson to the job, knowing that he kept up his association with Epstein after the businessman had served a jail term, which ended in 2009, for soliciting girls under 14.

Democrats rekindle Trump’s Epstein problem with ‘birthday note’Opens in new window ]

One MP said No 10 had appeared to view the scandal around Epstein and Mr Mandelson as “a silly internet conspiracy” rather than taking it seriously, while another said the “boys’ club” in Downing Street had rallied round him without considering the consequences.

Two Labour MPs, Bell Ribeiro-Addy and Kim Johnson, called for Mr Mandelson to quit.

Mr Mandelson has previously claimed not to have had a business relationship with Epstein and told the FT to “f**k off” when it questioned him about the financier.

However, in an interview earlier this week with the Sun, he said he had been deceived by Epstein’s “lies” and described the scandal as “like an albatross around my neck”. Epstein killed himself in jail in 2019 while awaiting further charges of trafficking young girls.

British ambassador to the United States Peter Mandelson and UK prime minister Keir Starmer  during a welcome reception at the ambassador's residence in Washington, DC, earlier this year. Photograph: Carl Court/PA WireBritish ambassador to the United States Peter Mandelson and UK prime minister Keir Starmer during a welcome reception at the ambassador’s residence in Washington, DC, earlier this year. Photograph: Carl Court/PA Wire Peter Mandelson pictured in October 1999 when making his first keynote address as the new Northern Ireland secretary. Photograph: Paul Faith/PA WirePeter Mandelson pictured in October 1999 when making his first keynote address as the new Northern Ireland secretary. Photograph: Paul Faith/PA Wire

At prime minister’s questions, Mr Starmer said “full due process was gone through when the appointment was made”.

Mr Starmer described Epstein as a “despicable criminal who committed the most heinous crimes and destroyed the lives of so many women and girls”.

“The ambassador has repeatedly expressed his deep regret for his association with him … I have confidence in him,” the prime minister said. – Guardian