Prime Minister Keir Starmer spoke in front of 10 Downing Street on Monday.June 22, 2026, 4:40 AMLONDON -- Prime Minister Keir Starmer announced on Monday he would resign as the leader of his party and as prime minister, setting the stage for the United Kingdom's seventh prime minister within a decade.Starmer, who said he spoke on Monday with King Charles, said he expected to remain in office until a successor was chosen from within his Labour Party."The question my party is asking now is whether I am best placed to lead us into the next general election," he said outside 10 Downing Street. "I have heard the answer of my parliamentary party to that question, and I accept that answer with good grace."Britain's Prime Minister Keir Starmer makes a statement on his future outside 10 Downing Street on the morning of June 22, 2026, in London.Henry Nicholls/AFP via Getty ImagesStarmer said he asked party leaders to open nominations for a successor on July 9. He did not give a date for his departure from 10 Downing Street, but said he expected a new prime minister to be in place by September, when Parliament returns from its summer recess.Starmer, who had lead Labour since 2020, was elected to lead the country in 2024. A formal challenge to his premiership had not yet begun as of Monday, but members of his party have in recent weeks pointed to Andy Burnham, the former mayor of Greater Manchester, as his potential successor.New Labour Party MP for Makerfield, Andy Burnham speaks to supporters and members of the media, the morning after his by-election victory, at Ashton Town FC, in Ashton in Makerfield, north-west England on June 19, 2026.Darren Staples/AFP via Getty ImagesBurnham, who won a special election on Friday to become a member of parliament representing Makerfield, was expected to be sworn in in the House of Commons on Monday. Popular ReadsMany in Starmer's Labour party had written to Starmer asking him to step down following local elections in May, during which saw the party lost more than 1,000 seats on local councils, results that were widely interpreted as a repudiation of Labour's performance to date by British voters.Members of staff bring the lectern outside 10 Downing Street on the morning of June 22, 2026, in London as Britain's Prime Minister Keir Starmer prepares to make a statement on his future.Henry Nicholls/AFP via Getty ImagesStarmer long said he intended to see out his full five-year term, which began with his party's 2024 landslide election victory that ended 14 years of Conservative Party government and delivered Labour a historic majority in the House of Commons.ABC News' David Brennan contributed to this report.