Theresa May has fired the starting gun on a leadership race to find a new prime minister by confirming she will leave Downing Street within weeks.
In an emotional statement outside Number 10, May said she will resign as Conservative leader on 7 June, but stay on as prime minister until her successor is elected.
She made the announcement following a meeting with Sir Graham Brady, chairman of the 1922 Committee of Conservative backbenchers.
May said it had been "the honour of my life" to be prime minister but admitted she had failed to get her Brexit deal over the line.
"I tried three times, I believe it was right to persevere even when the odds against success seemed high," she said. "But it is now clear to me that it is in the best interest of the country for a new prime minister to lead that effort.
"So I am today announcing I will resign as leader of the Conservative and Unionist Party on Friday 7 June so that a successor can be chosen."
In a clear warning to her successor not to pursue a no-deal Brexit, May said "compromise is not a dirty word".
"It is and will always remain a matter of deep regret to me that I have not been able to deliver Brexit," she said. "It will be for my successor to seek a way forward that honours the result of the referendum.
"To succeed, he or she will have to find consensus in parliament where I have not. Such a consensus can only be reached if those on all sides of the debate are willing to compromise."
Her departure became inevitable following a cabinet revolt over the Withdrawal Agreement Bill she had hoped to put to a Commons vote next month.
Ministers told her they could not support the legislation because of a clause giving MPs a vote on another EU referendum.
Foreign secretary Jeremy Hunt told the prime minister in a meeting on Thursday that she should scrap the WAB rather than force loyal Conservative MPs to support it when it stood no chance of passing.
Home secretary Sajid Javid told May he could not support the bill unless the referendum section was ditched.
May was given a stay of execution on Wednesday when the 1922 Committee executive gave her the chance to step down voluntarily rather than face the humiliation of a second vote of no confidence.
The Conservative leadership race will officially begin on 10 June and is expected to last until the end of July.
Boris Johnson is the clear favourite to replace May, but a large number of Conservative MPs are committed to ensuring he does not succeed.
International development secretary Rory Stewart and former work and pensions secretary Esther McVey have already confirmed that they will throw their hats into the ring, with Hunt, Javid, former Brexit secretary Dominic Raab and ex-leader of the House of Commons Andrea Leadsom among those also expected to take part in the contest. Leadsom resigned on Wednesday, saying she could not support the prime minister’s revised plan.
The list of candidates will be whittled down to two by Tory MPs, before the party's 125,000 members vote on who should be the next prime minister.