Keir Starmer has seen off a major Labour rebellion over a bid to force a parliamentary investigation into his appointment of Peter Mandelson , but many of his own MPs warned he was running out of political capital.

After Downing Street deployed its full weight to force Labour MPs to block a referral to the privileges committee over the scandal, some angrily accused Starmer of leaving them facing accusations of a “cover-up”.

Previously loyal MPs warned the prime minister to tread carefully, particularly after what are expected to be a damaging set of election results for Labour next week.

“He’s in the last-chance saloon and the last few days haven’t improved his prospects of survival,” one minister said, while another added: “Keir only has so much credit in the bank with the backbenches now, so he needs to spend it wisely.”

On a day of high jeopardy on Tuesday, Starmer’s former chief of staff, Morgan McSweeney, and the Foreign Office’s former permanent secretary, Sir Philip Barton, prompted yet more…