Andy Burnham will officially launch his campaign as the Labour candidate in the Makerfield by-election on Friday morning, as he looks to secure a return to parliament after nine years.
It is widely believed that Mr Burnham, who is currently the mayor of Greater Manchester, is looking to challenge Sir Keir Starmer for the Labour leadership if he becomes an MP.
The prime minister has made clear he has no intentions to step down and said on Thursday he would campaign alongside Mr Burnham in the by-election, which will be held on 18 June.
“I’ve said to the whole Labour movement that I want everybody to be involved in the campaign, whatever other discussions are going on, it’s really important – that’s a straight fight between Labour and Reform,” Sir Keir said.
But current polling of Labour party members shows that Mr Burnham would win comfortably if there was a leadership contest between the pair.
Meanwhile, Sir Keir’s government is looking to seize back control of the headlines after a turbulent two weeks with Rachel Reeves announcing a series of measures to help ease cost of living pressures for Britons on Thursday.
