UK Prime Minister Keir Starmer is facing mounting pressure from within his own party, as Labour MPs warn his leadership could be under threat following intense backlash over the appointment of Peter Mandelson as the United States ambassador.

Anger erupted in Parliament after it emerged that Starmer had been aware of Mandelson’s past friendship with convicted sex offender Jeffrey Epstein prior to approving the appointment. The controversy brought the government to the brink of a Commons defeat, only averted after a late amendment was agreed to during a heated debate.

The amendment, brokered by senior Labour figures Meg Hillier and Deputy Prime Minister Angela Rayner, calls for the release of official documents detailing the process behind Mandelson’s appointment and the extent of his relationship with Epstein. MPs say the disclosure of those documents potentially delayed due to an ongoing police investigation could spark a formal leadership challenge.

Several Labour MPs described the mood within the party as “toxic,” with one former minister calling it the worst day for the government to date. Another MP warned that trust in the prime minister was “finite,” raising doubts about continued support in any future confidence vote. Notably, concerns were reportedly strongest among MPs traditionally seen as loyal to Starmer.

Tensions escalated further during Prime Minister’s Questions when Starmer acknowledged that he had prior knowledge of Mandelson’s association with Epstein, a moment MPs described as visibly shifting the atmosphere in the chamber. Downing Street later clarified that the prime minister was only aware of information already in the public domain.

Critics within Labour argue that the appointment was politically indefensible, drawing comparisons to past scandals that proved fatal to previous governments. As pressure builds, the episode has intensified scrutiny of Starmer’s judgment and leadership at a critical moment for the Labour government.