Theresa May has said she will quit as Conservative leader on 7 June, paving the way for a contest to decide a new prime minister.
In an emotional statement, she said she had done her best to deliver Brexit and it was a matter of “deep regret” that she had been unable to do so.
Being prime minister had been the “honour of my life”, she said.
Mrs May said she would continue to serve as PM while a Conservative leadership contest takes place.
It means she will still be prime minister when US President Donald Trump makes his state visit to the UK at the start of June.
Mrs May announced she would step down as Tory leader on 7 June and had agreed with the chairman of Tory backbenchers that a leadership contest should begin the following week.
Boris Johnson, Esther McVey and Rory Stewart have said they intend to run for the party leadership, while more than a dozen others are believed to be seriously considering entering the contest.
The prime minister has faced a backlash from her MPs against her latest Brexit plan, which included concessions aimed at attracting cross-party support.