The Prime Minister’s voice broke as she said she would quit as Leader of the Conservative Party in just two weeks on 7 June.
Theresa May said she had “done [her] best” to get her Withdrawal Agreement through parliament and to give people what they had voted for in the Brexit referendum of 2016.
“I believe it was right to persevere even when the odds against success seemed high.”
But she acknowledged she had failed, saying: “It is and will always remain a matter of deep regret to me that I have not been able to deliver Brexit.”
Watched by her husband Philip and her closest aides, she said: “It is now clear to me that it is in the best interests of the country for a new Prime Minister to lead that effort.
“So I am today announcing that I will resign as Leader of the Conservative and Unionist Party on Friday the 7 June.”
Fighting back tears, she said she was leaving the job “with no ill will”, adding that she was “the second female prime minister but certainly not the last”.
Concluding her resignation statement, Mrs May broke down as she said it had been “the honour of my life” to serve “the country that I love”.
Mrs May’s announcement comes after a showdown this morning with Sir Graham Brady, chairman of the 1922 committee of Conservative MPs.
It also marks the end of a frenzied week, after more MPs demanded her immediate resignation and a senior cabinet minister quit.
Brexiteer Andrea Leadsom said she could not support the revamped Withdrawal Agreement Bill because it did not respect the referendum result.
The Prime Minister’s resignation now starts a contest to become Britain’s next Prime Minister.
She will remain as a caretaker Prime Minister until the new leader is chosen and this could take several weeks.
One of the candidates to replace her, Dominic Raab, described Mrs May as “dignified as ever…she remains a dedicated public servant”.
Mrs Leadsom said Mrs May’s speech was “an illustration of her total commitment to country and duty”.
Mrs May’s Chief of Staff Gavin Barwell said: “As the PM’s Chief of Staff for the last two years, I have seen at first hand her commitment to public service and her incredible resilience as she has confronted the biggest challenge any British Government has faced since the Second World War. It has been an honour to serve her.”
Meanwhile, the UK is currently due to leave the European Union on 31 October, but Parliament has yet to approve the terms.