Angela Rayner has demanded that Andy Burnham be allowed to stand as an MP, opening the door to a potential leadership challenge against Sir Keir Starmer by the Manchester mayor.

The Prime Minister’s former deputy said that his decision to block Mr Burnham from standing for Parliament earlier this year was a “mistake that the leadership of our party should put right”.

In an address to the Communications Workers Union hours after Sir Keir delivered his reset speech, Ms Rayner said: “We as a party have to do better than this. And we can only prove we mean our Labour values by putting the common interest ahead of factionalism.

“And we can start by accepting that Andy Burnham should never have been blocked. It was a mistake that the leadership of our party should put right.”

Mr Burnham was prevented from standing as the Labour candidate in the Gorton and Denton by-election in February by Sir Keir and his allies on Labour’s ruling body.

The Prime Minister’s opponents accused him of running scared from a potential leadership challenge.

Ms Rayner’s renewed call for Mr Burnham to return to Westminster came as a growing number of Labour MPs demanded that Sir Keir resign despite his efforts to move on from the party’s disastrous local election results last week.

Shortly after Sir Keir’s speech, Catherine West, a leading Labour rebel who previously suggested that she could run against the Prime Minister, demanded that he resign by September.

That timeline would favour Mr Burnham as he is currently ineligible to run for the Labour leadership because he is not an MP. A slower leadership election would give him time to find a seat to stand in and contest a by-election.

A shorter contest would favour Wes Streeting, the Health Secretary, who represents the Right wing of the party.