Liz Truss said on Thursday she was resigning as prime minister, brought down by her economic programme that sent shockwaves through the markets and divided her Conservative Party just six weeks after she was appointed.
A leadership election will be completed within the next week.
Speaking outside the door of her Number 10 Downing Street office, Truss accepted that she could not deliver the promises she made when she was running for Conservative leader, having lost the faith of her party.
"I recognise though, given the situation, I cannot deliver the mandate on which I was elected by the Conservative Party. I have therefore spoken to His Majesty the King to notify him that I am resigning as leader of the Conservative Party," she said.
"This morning I met the chairman of the 1922 Committee, Sir Graham Brady. We've agreed that there will be a leadership election to be completed within the next week. This will ensure that we remain on a path to deliver our fiscal plans and maintain our country's economic stability and national security."