FILE PHOTO: U.S. President Donald Trump shakes hands with Britain's ambassador to the United States, Peter Mandelson, after announcing a trade deal with the U.K., in the Oval Office at the White House in Washington, D.C., U.S., May 8, 2025. REUTERS/Leah Millis/File Photo
FILE PHOTO: A person walks past a poster with a photograph of Donald Trump, now serving as the U.S. President, and disgraced financier and sex offender Jeffrey Epstein, protesting Trump’s upcoming state visit to the UK, in London, Britain, September 3, 2025. REUTERS/Isabel Infantes/File Photo

LONDON (Reuters) - Britain's ambassador to the U.S., Peter Mandelson, has said he deeply regrets ever meeting convicted sex offender Jeffrey Epstein and that he had carried on that association "for far longer than I should have done".

Mandelson, a veteran Labour politician who was key to the party's success under former leader Tony Blair, has come under scrutiny over his relationship with Epstein after a birthday book was released including a letter purportedly from the now ambassador describing Epstein as "my best pal".

In an interview with Britain's Sun newspaper released on Wednesday, Mandelson said he felt a "profound sense of sympathy for those people, those women who suffered as a result of his behaviour and his illegal criminal activities".

"I feel a tremendous sense of regret not only that I met him in the first place, but that I continued the association and I took at face value the lies that he fed me and many others," he said, describing Epstein as a "charismatic criminal liar".

The release of the document and others involving Epstein, who died by suicide in prison in 2019, have brought renewed attention to an issue that has implicated others, including U.S. President Donald Trump and Britain's Prince Andrew.

British Prime Minister Keir Starmer on Wednesday gave Mandelson his backing after the revelations.

"The ambassador has repeatedly expressed his deep regret for his association with (Epstein)," Starmer told parliament when asked if he still had confidence in Mandelson.

"He's right to do so. I have confidence in him, and he's playing an important role in the UK-U.S. relationship."

When appointed late last year, Mandelson became the first political appointee to the role as ambassador to the U.S. in almost half a century, marking a high-profile return for a man once dubbed the "Prince of Darkness" by the media for his behind-the-scenes manoeuvring in former Labour administrations.

No stranger to controversy, he was twice forced out of cabinet over separate scandals, but in the Sun interview he said he, and many others, had simply been taken in by Epstein.

"I regret very much that I fell for his lies, that I fell, and accepted assurances that he had given me about his indictment," he said.

"With hindsight, with fresh information many years later, we realised that we had been wrong to believe him ... I regret very much indeed, I felt it like an albatross around my neck since his death."

(Reporting by Elizabeth Piper and Muvija M; Editing by Alex Richardson)