British Prime Minister Keir Starmer’s chief of staff, Morgan McSweeney, resigned on Sunday after taking responsibility for advising Starmer to appoint Peter Mandelson as U.S. ambassador, a decision that has drawn intense scrutiny following disclosures about Mandelson’s ties to Jeffrey Epstein.

After new files revealed the depth of the Labour veteran's relationship with the late sex offender, Starmer is facing what is ‌widely seen as the gravest crisis of his 18 months in power over ‍his decision to send Mandelson to Washington in 2024.

The loss of McSweeney, 48, a strategist who was instrumental in Starmer's rise to power, is the latest in a series of setbacks, less than two years after the Labour Party won one of the largest parliamentary majorities in modern British history.

Starmer in the firing line

With polls showing Starmer is hugely unpopular with voters after a series of embarrassing U-turns, some in his own party are openly questioning his judgment and his future, and it remains to be seen whether McSweeney's exit will be enough to silence critics.