Greater Manchester Mayor Andy Burnham is expected to challenge Sir Keir Starmer’s leadership within a fortnight of the Makerfield by-election if he succeeds in his bid to return as an MP, The i Paper can reveal.

Cabinet ministers are braced for Burnham to launch a contest to try to succeed the Prime Minister by the end of June or early July.

Senior ministers are war-gaming how quickly Burnham will declare his candidacy for Labour leader. They are weighing up whether he needs a period to get to know colleagues in Parliament and establish a clear programme for government, while simultaneously convincing Starmer to retire quietly.

“I think there’s an expectation that if he wins, then things will move,” a Cabinet source said. “There’ll be some discussion about what the timescale is. Then, in exchange for a timescale, it’ll be: will Keir go graciously or not?”

“Andy hasn’t given up on the mayoralty in Manchester – where he can do things – to sit in the background. He also hasn’t stood there to be brought into the collective responsibility of the Cabinet, certainly not under its current stewardship. And he certainly isn’t going to let someone beat him to the job,” they added.