Liz Truss has resigned as prime minister after 45 days in office marked by turmoil, triggering the second Tory leadership election in four months.
Truss said her successor would be elected by next week after a rebellion by Tory MPs forced her to quit.
Chancellor Jeremy Hunt said he would not run in the contest but other senior Tories are considering bids.
Tory MPs revolted against Truss after a series of U-turns on her economic plan sapped her of authority.
In a brief speech outside Downing Street, Truss said the Conservative Party had elected her on a mandate to cut taxes and boost economic growth.
But given the situation, Truss said: “I recognize that I cannot deliver the mandate on which I was elected by the Conservative Party.”
Truss said she would remain in post until a successor formally takes over as party leader and is appointed prime minister by King Charles III.
Hunt – who was appointed chancellor last week – has said he will not stand in the leadership contest to be the next prime minister, but none of the candidates who stood against Truss in the previous contest have indicated whether they’ll be standing.
Sir Graham Brady, the chairman of the 1922 backbench committee of Conservative MPs, said it would be possible to conclude a leadership ballot by Friday next week.
He said he expected Conservative members to be given a say on who succeeds Truss, but would set out further details later.
And he sidestepped questions about whether one or two candidates would be likely to run, telling reporters: “The party rules say there will be two candidates unless there is only one candidate.”
Agencies