Former prime minister Gordon Brown has backed Sir Keir Starmer, telling Sky News Labour has got to give him a chance.
The Labour leader, who succeeded Jeremy Corbyn in 2020, has come in for criticism in recent days over the party’s mixed performance in elections across the UK.
This included losing the Hartlepool by-election to the Conservatives – the first time the seat has turned blue since its formation more than 50 years ago.
Sir Keir has also attracted the ire of many within Labour for his handling of a shadow cabinet reshuffle.
Having pledged to take "full responsibility" for Labour’s reverse in Hartlepool, one of his first moves was to sack Angela Rayner as party chair.
It sparked a furious backlash, although Ms Rayner was later appointed shadow first secretary of state, shadow secretary of state for the future of work and shadow chancellor to the Duchy of Lancaster.
Mr Brown, who served as Labour leader and prime minister from 2007 to 2010, said Sir Keir should be given time.
"Starmer wants to go for change, he wants to make the Labour Party face up to all the problems that this country faces and have solutions to them, and we’ve got to give him the space, the power and support to make these changes that are necessary," he said.
"You can’t go back to 1997, you can’t go back to the manifesto of 2019, you’ve got to move forward.
"I think Keir is trying to move the party forward – he had success in the elections and he had reverses, and you can see the electoral geography of Britain has been changing.
"But we’ve got to give him the chance to set out his response to these seismic changes that are shattering traditional assumptions right across the West."
Re-elected Greater Manchester mayor Andy Burnham set tongues wagging at the weekend, when he did not dismiss out of hand suggestions he could mount a bid for the Labour leadership in the future.
He told Sky News the party should "get in touch" if it were "ever to feel it needed me".
Speaking on Monday, Mr Burnham criticised the handling of Ms Rayner’s sacking.
"I didn’t like the way that was handled, I’ll be honest," he said.
"I didn’t see why we were getting a negative story on Saturday night when myself and Steve Rotheram and other people around the country had good victories to celebrate, so that wasn’t right, but I don’t think the way Angela was treated was right.
"But it’s been resolved and we move on from this morning."
Asked if he had designs on the party’s top job in the future, London mayor Sadiq Khan told Sky News: "No. Keir is our leader, Keir is my leader.
"He’s doing a great job and has my full support."
In his Sky News interview Mr Brown also discussed Scottish independence at length.
He claimed Nicola Sturgeon has yet to address the "difficult issues" that leaving the Union would create, such as the future of the pound, pensions and the border.
He said the thinktank he has helped set up – Our Scottish Future – had carried out polling which showed that "only 20%" of Scots want a second referendum this year or next year.
"Scottish people want change, they’re clear about that. But nobody wants an immediate referendum," Mr Brown said.
He added that "gives us time" to examine how the UK works and "whether it can be more accommodating".
In addition, Mr Brown said the issues that leaving the Union would throw up could be looked at to ascertain "what independence really means" and "what really does it add up to".
In the wake of this week’s Scottish Parliament elections, Ms Sturgeon has declared that another referendum is a "matter of when, not if".
The SNP fell one seat short of a majority, but with the Greens there is a pro-independence majority in Holyrood.
Ms Sturgeon has promised to introduce legislation for another vote, but this could be challenged by the UK government in court.
Prime Minister Boris Johnson has repeatedly said he will not allow a second referendum to take place.
The UK government agreed to hold the first vote in 2014, which saw Scottish voters reject independence.
However, Ms Sturgeon argues that the 2016 EU referendum – which saw the UK as a whole vote for Brexit but Scotland back Remain – has changed things.
The current stand-off between Edinburgh and London raises questions about how Ms Sturgeon will proceed if it continues.
Mr Brown acknowledged that the SNP had a right to push for another referendum, but said it has "got to be done by a legal and acceptable process".