Theresa May has announced she will resign as Conservative Party leader on June 7, following a furious backlash to her last-ditch Brexit plan.
Speaking in Downing Street on Friday morning, May said: “I have done my best.
“It is and will always remain a matter of deep regret to me that I have not been able to deliver Brexit,” she said.
Her voice cracked with emotion as she said it had been the “honour of my life” to serve “the country that I love” for the last three years.
May will remain as prime minister while the party holds a leadership contest beginning on June 10.
Party chairman Brandon Lewis said May’s successor is expected to be announced by mid-July.
The new prime minister will then have just over three months until the UK is set to leave the EU on October 31.
May was finally ousted by her party following a cabinet revolt over her decision to offer MPs a vote on whether to hold a second referendum.
Jeremy Corbyn said May was “right” to resign and said whoever replaced her must call an “immediate” general election.
Boris Johnson, the Brexiteer former foreign secretary, is currently seen as the frontrunner to replace her.
But several other senior Tories, including ex-Brexit Secretary Dominc Raab, Foreign Secretary Jeremy Hunt, Home Secretary Sajid Javid and Environment Secretary Michael Gove are all expected to throw their hat into the ring.
Speculation was also rife in Westminster that Sir Graham Brady, the chairman of the backbench Tory 1922 committee is also considering standing.
Ken Clarke, the former Tory chancellor and veteran MP, predicted the contest would be “six weeks of chaos”.
Tory MPs will whittle down the leadership candidates to the final choices by the end of June.
The two candidates will then take part in a series of hustings around the UK before party members pick a winner.
In a statement, Lewis said: “We are deeply conscious that the Conservatives are not just selecting the person best placed to become the new leader of our party, but also the next prime minister of the United Kingdom. That is a solemn responsibility, particularly at such an important time for our nation.
Andrea Leadsom, whose resignation as Commons leader signalled the end of May’s time in office, praised the PM’s “dignified speech” as an “illustration of her total commitment to country and duty”.
Steve Baker, the leading backbench Tory Brexiteer who led efforts to oust May, said it was a “sad but necessary day”.
Work and Pensions Secretary Amber Rudd said the PM had “shown great courage”.
“She is a public servant who did all she could to bring Brexit to a resolution. Her sense of duty is something everyone should admire and aspire to,” she said.
Nigel Dodds, the DUP’s Westminster leader who has been propping up the Conservative government, said while he had “differences” with May he found her to be “very courteous and pleasant to work with on a personal basis”.
Nigel Farage, who is expecting his new Brexit Party to emerge as the winners of Thursday’s European elections, said it was “difficult not to feel” for May but said she “misjudged the mood of the country and her party”.
“Two Tory leaders have now gone whose instincts were pro-EU. Either the party learns that lesson or it dies,” he tweeted.
European Commission president Jean-Claude Juncker “followed prime minister May’s announcement this morning without personal joy”, a spokesman said.