LONDON -- Andy Burnham will officially become British prime minister on Monday -- the country's seventh leader in 10 years -- having already been elected as the leader of the country's Labour Party last week.Burnham, who until recently was serving as the Mayor of Greater Manchester, will succeed outgoing Prime Minister Keir Starmer. Posting on X on Monday, Starmer wrote, "The test of any Prime Minister is: do you leave your country in a better place than you found it? I'm proud that the answer is yes."Starmer will travel from the prime minister's official residence in Downing Street to Buckingham Palace on Monday morning, where he will formally inform King Charles III of his resignation. Burnham will then travel to the palace, where the king will ask Burnham to form a government.The new prime minister is then expected to return to Downing Street, where he will address the assembled press. Burnham will then enter Downing Street and begin appointing cabinet ministers.Andy Burnham reacts as he speaks after being confirmed as the Labour Party's new leader and the country's next prime minister, in London, U.K., on July 17, 2026.Henry Nicholls/via ReutersStarmer announced that he would step down in June, following months of domestic political turmoil. Despite leading Labour to a historic majority in parliament in the 2024 general election, Starmer faced persistent external and internal criticism over his perceived failure to deliver rapid change after 14 years of Conservative Party rule in Britain.Many in Starmer's party had written to the prime minister asking him to step down following local elections in May, which saw the party lose more than 1,000 seats on local councils, results that were widely interpreted as a repudiation by British voters of Labour's performance under the prime minister's leadership.Starmer long said he intended to see out his full five-year. Announcing his resignation in June, Starmer said, "The question my party is asking now is whether I am best placed to lead us into the next general election. I have heard the answer of my parliamentary party to that question, and I accept that answer with good grace."Burnham was the only candidate in the subsequent leadership election, ultimately winning nominations from 379 of the 403 Labour members of parliament -- of the 650 MPs in total -- in the House of Commons.In accepting the leadership of Labour last week, Burnham said his mission was "to bring back hope" and address decades of economic inequality plus falling living standards. Ukrainian President Volodymyr Zelenskyy (R) presents The Order of Freedom to British Prime Minister Keir Starmer in the gardens of the Presidential Palace in Kyiv, Ukraine, on July 16, 2026, as Starmer visited Ukraine for the last time before leaving office.Stefan Rousseau/Pool PA via AP"We must recognize that this generation of politicians -- myself included -- have failed to challenge a political culture and an economic model that simply doesn't work well enough for ordinary people," he said.Burnham will become the seventh leader to take the reins of the country in 10 years, a reflection of the political and economic turbulence that has beset the country since the Brexit vote in 2016.Popular ReadsThe incoming prime minister said he would also make British politics "less toxic, adding, "I will work to build a new politics. The country is crying out for it."Burnham, 56, was born in the Lancashire region of northern England. Burnham started out as a journalist, writing for trade magazines, before transitioning to work as a Labour parliamentary researcher while in his early 20s.Burnham rose through the party ranks before being elected as the MP for his hometown of Leigh, in Greater Manchester, in 2001. He held that seat -- and several cabinet positions -- until 2017, after which he left parliament to become the mayor of Greater Manchester.Burnham is associated with the center left of the Labour Party, and has described himself as a socialist. Burnham's time as Manchester mayor saw him emerge as a major proponent of shifting investment and political power out of London, and earned him the nickname "the King of the North."ABC News' Kevin Shalvey contributed to this report.