Sir Keir Starmer has said he would offer Andy Burnham a “big role in government” if he is elected as an MP in the Makerfield by-election this week. 

The Prime Minister indicated that the current Manchester mayor would be given a Cabinet role as he said he had “spoken to him many times in recent weeks”. 

Starmer also recalled that he backed Burnham to become Labour leader in 2015 and said he was a “huge asset” to the party.

When asked whether he would offer Burnham a role in the Cabinet in an interview with Sky News, Starmer said: “Yes, I want him to have a big role in government.”

His comments appear to lay down the gauntlet to Burnham, who said he would look to become Labour leader – and therefore Prime Minister – if he wins the by-election on Thursday. 

Burnham has framed his campaign around changing the party as he has talked up a series of policies that would go against Starmer’s premiership.  

The Prime Minister, however, has remained defiant, batting away questions about leadership speculation and insisting he would stand again in any contest. 

In a seeming message to MPs looking to oust him rapidly, Starmer also told journalists that a snap election for the mayoralty in Greater Manchester would require close attention. 

“What happens is we’re immediately tipped into a Manchester mayoral contest by-election, one of the biggest by-elections that we’ve ever fought, because of the scale of it,” Starmer said.

“And it’s really important to my mind that the whole of the Labour Party and Labour movement focuses on that, which is the next most immediate task.”

Starmer in bunker mode

He added: “I don’t think there should be a challenge. I think history, particularly the last government, shows that that isn’t a successful way for a government to behave.

“If there is a challenge, then I intend to fight. “I’m not going to walk away from that, and I’ve been clear and consistent about that.”

The by-election is set to be a crunch moment for Labour and the country’s leadership, with rumours swirling over whether Burnham can clinch victory in Makerfield and how early he would attempt to trigger a leadership contest. 

On Tuesday, former health secretary Wes Streeting also built on his campaign to become Labour leader as he delivered a speech focusing on driving growth by passing legislation to allow critical infrastructure to be built quickly.