Keir Starmer has announced his resignation as prime minister.
Speaking outside No.10, Starmer said he spoke to the King this morning to inform him of his decision to step down as PM.
Explaining his decision, Starmer said he had "answered" the question about who was best placed to change the Labour Party, take it into power and "begin the vital work of improving lives for millions of people". But he said the question the party was now asking was whether he was best placed to lead it into the next general election and that he had "heard the answer" to that question.
"And I accept that answer with good grace," Starmer said. "Every decision I've taken has been about putting the country I love first. That is why I will resign as leader of the Labour Party."
As part of his resignation speech, Starmer thanked his "brilliant No.10 staff and our country's extraordinary civil service who dedicate their lives to public service".
Starmer said he will ask the Labour Party's National Executive Committee to set out a timetable for appointing his successor, with nominations opening on 9 July and to be completed by the summer recess.
"In the case of a contest, this will ensure a new leader is in place before parliament returns in September," Starmer said.
Starmer said he will remain in post as PM until a contest is complete and do "everything" he can to ensure an orderly handover of power.
"I will also give my successor my full and unequivocal support, knowing that they will inherit a Britain that is far stronger and fairer than the one I inherited two years ago, better prepared for the challenges ahead, and better able to ensure the Labour Party secures a second term in office, " Starmer said.
In the event of no contest, Starmer's successor could be in place by mid-July, with reports suggesting new MP and former Greater Manchester mayor Andy Burnham is the strong favourite.
Following Starmer's announcement, Burnham confirmed he would stand for PM.
He also received the backing of former health secretary Wes Streeting, who had earlier this year said he would stand in a leadership election.
"Having spoken at length with Andy in recent days, I'm convinced that there is a place for those ideas under his leadership; that he is committed to building an inclusive party that draws on the best of our political traditions; and that he can win the fight of our lives against the forces of nationalism," Streeting said.
"We could spend the summer exaggerating small differences, or we can roll up our sleeves and help him to deliver the change our party and our country needs. That is the choice that I am making and I hope that everyone else will back Andy, too."