The UK prime minister has announced that he will step down from his post and will no longer lead the Labour Party UK Prime Minister Keir Starmer has announced that he will resign from his post and will step down as the leader of the Labour Party. In an address outside 10 Downing Street on Monday, Starmer said he already informed King Charles III of his decision and asked the Labour Party to lay out a timetable to elect a new leader by September, adding that he will remain in his post until then.