Peter Mandelson, the UK ambassador to the US, was dismissed on Thursday after embarrassing details of his friendship with scandal-ridden American financier Jeffrey Epstein were published.
A government statement said Prime Minister Keir Starmer had asked the Foreign Office to withdraw Mr Mandelson as ambassador.
It referred to historic emails that show the depth of Mr Mandelson's support of Epstein, even after he had been convicted of soliciting underage sex.
Mr Mandelson’s friendship with Epstein was well known, but the newly published emails showed that the relationship continued after the crimes he committed had emerged.
“The emails show that the depth and extent of Peter Mandelson’s relationship with Jeffrey Epstein is materially different from that known at the time of his appointment,” the statement said. “In particular, Peter Mandelson’s suggestion that Jeffrey Epstein’s first conviction was wrongful and should be challenged is new information.
“In light of that, and mindful of the victims of Epstein’s crimes, he has been withdrawn as ambassador with immediate effect.”
Mr Mandelson, a veteran Labour politician who was key to the party's success under former leader Tony Blair, came under heavy scrutiny over his relationship with Epstein after a birthday book was released recently.
It included a letter purportedly from Mr Mandelson describing Epstein as his “best pal”.
US President Donald Trump is to make an unprecedented second state visit to the UK next week, and Mr Mandelson was viewed as having played a key role in building a relationship between the UK government and the White House.
Mr Mandelson spent almost an hour in the Oval Office with Mr Trump on Wednesday, when he accompanied Scottish First Minister John Swinney at a trade meeting.
Mr Trump has also been dogged by his links to Epstein, although he said they had a falling-out two decades ago. Congressional Democrats on Monday released a sexually suggestive letter to Epstein that was purportedly signed by Mr Trump, although he has denied it is his signature.
Mr Starmer had defended Mr Mandelson until the emergence of the emails, insisting he had gone through a proper vetting process.
“I have confidence in him, and he is playing an important role in the UK-US relationship,” he told the House of Commons on Wednesday.
Health Secretary Wes Streeting said he was “completely disgusted” by messages Mr Mandelson sent to Epstein.
“I’ve obviously seen overnight the latest tranche of messages and was completely disgusted by them,” he said.
Epstein took his own life while awaiting trial on sex-trafficking charges in 2019.
