(Sharecast News) - Andy Burnham pledged to bring about the "biggest changes in 40 years" on Monday, as he became the UK's latest prime minister.

Giving his first speech in the role outside 10 Downing Street, the former Greater Manchester mayor said he was "acutely conscious that I am the sixth person in the last ten years to walk up this street", making him the seventh prime minister since David Cameron resigned after the Brexit referendum in 2016.

That made this "a moment for reflection and new resolution," he said. "It requires my generation of politicians to raise our game and rise to the new challenge.

"Britain needs to show the world that we can regain our stability...and that is our challenge - to make politics work, to make it work better. We have not been good enough and we need to be better. We will be."

He promised a "circuit-breaker" that would usher in the "biggest changes in the last 40 years, a new political model and a new economic model". He argued that Britain had taken "some wrong turns" in the 1980s that had never been corrected, including centralising political power, privatisation and de-industrialisation.

Burnham said he intended to publish a ten-year plan later in the year, but on Tuesday would set out how he intended to give people "some breathing space now".

The short speech was, however, devoid of specifics, apart from a commitment to end rough sleeping.

Burnham replaced Keir Starmer, who stepped down earlier in the day. Two years ago Starmer oversaw Labour's landslide general election victory but he lost the support of the parliamentary party, paving the way for Burnham to take over. Burnham, who had twice previously run and failed to become party leader, was elected as an MP last month and confirmed party leader last week. There were no other rivals for the role.

Speaking before he headed to Buckingham Palace, Starmer said he was closing "the book on my time on prime minister. My work is done."

He continued: "As I pass the baton to Andy Burnham, I wish him every success. He has my full support."

Burnham will now announce his cabinet, with current home secretary Shabana Mahmood expected to become chancellor and energy secretary Ed Miliband - who had also been touted as a possible contender for Number 11 - becoming foreign secretary. Angela Raynor and Lucy Powell are both likely to return to cabinet.

Rain Newton-Smith, chief executive of the Confederation of British Industry, congratulated Burnham. But she added: "Ambitious plans to improve the livelihoods of people across the country must be matched by action to get businesses thriving once again."

James Smith, developed markets economist, UK, at ING, said: "Britain's new prime minister's bold ambition is constrained by tight fiscal rules and a commitment not to raise major taxes. An understated autumn budget looks like the growing consensus. But don't rule out bigger plans on anything from capital investment to the fiscal rules - or, crucially, a snap general election."

Kathleen Brooks, research director at XTB, said: "As Burnham steps into the role, his agenda will come face-to-face with reality. The oil price is rising and another flare of tensions between the US and Iran are threatening to worsen the UK's cost of living crisis that Burnham is keen to alleviate.

"Latest polls suggest that he has lost the support of southern voters and he will also face questions of legitimacy, especially if he breaks Labour's 2024 manifesto pledges."