LONDON (AFP)

Andy Burnham will on Monday become Britain's seventh prime minister in a decade, with an in-tray overflowing with challenges that have trounced his predecessors and little time to make his mark.

The new leader takes over from Keir Starmer just two years after the outgoing prime minister led Labour to power in a landslide election victory after 14 years of Conservative rule.

After being asked by King Charles III to form the next government, Burnham, 56, is due to make his first speech Monday outside 10 Downing Street shortly after Starmer has said his farewells.

He will set out "priorities for restoring confidence in government and giving Britain more breathing room" amid the cost-of-living crisis, his team said. Delivering growth and devolving power to regional communities are also expected to feature.

An announcement on his senior cabinet appointments is also expected on Monday with all eyes on who will replace Rachel Reeves as finance minister.

The former mayor of Greater Manchester, nicknamed the "King of the North", has been parachuted in by the Labour Party, after Starmer resigned last month.

Deputy Labour Party leader Lucy Powell said on Sunday Burnham's mayoral experience away from the London centre of government meant he understood the "bigger, bolder measures" needed to deliver on Labour's election manifesto promises.

Among Burnham's most urgent challenges will be the economy, high government borrowing costs, and a ballooning welfare bill. Unpredictable energy prices due to the US-Iran war also threaten to buffet his premiership.

Starmer announced that he would resign as prime minister and Labour Party leader in late June. But Burnham, who only returned as a member of parliament four weeks ago, has little room to manoeuvre amid sluggish economic growth, high public debt, and strict financial rules requiring him to balance government spending against tax revenue.

Monday's handover will begin with Starmer visiting Buckingham Palace to formally tender his resignation to the king before making a brief statement outside 10 Downing Street.

Burnham will then make his own trip to Buckingham Palace, before his first speech as prime minster which will be a moment of "reflection and resolution," he will say, stressing Britain must be honest about the challenges it faces.

Burnham was an MP between 2001 and 2017, serving as a minister the governments of Tony Blair and Gordon Brown. He has since reinvented himself as a man of the people, melding a relaxed, folksy style with slick social media videos.

But he has only three years to turn things around, with political party Reform tipped in polls to win the next general election expected in 2029.

Burnham told supporters on Friday his Labour takeover was the "last chance" for the party to get things right. Burnham has insisted he has a "plan".

His first policy announcement came on Saturday when he scrapped Starmer's flagship nationwide digital ID scheme, estimated to cost £1.8 billion over three years.

A spokesperson said the time and resources would be diverted "to where it's most needed, such as helping with the cost of living".