Britain's Theresa May announced her resignation as prime minister on Friday morning, drawing her turbulent three-year premiership to an abrupt end.

She will step down as Conservative Party leader on June 7.

In an emotional speech outside 10 Downing Street, May said she had "done everything" she could to convince members of Parliament to back the Brexit withdrawal agreement she had negotiated with the European Union. But, she said it was with "deep regret" that she had ultimately failed to reach a consensus among lawmakers.

"I believe it was right to persevere even when the odds against success seemed high, but 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," May said at a hastily arranged press conference.

"I will shortly leave the job that it has been the honor of my life to hold. The second female prime minister but certainly not the last."

"I do so with no ill will but with enormous and enduring gratitude to have had the opportunity to serve the country I love," May said, her voice shaking.

Sterling briefly rose 0.5% to climb above $1.27 shortly after May's statement, before paring gains as investors digested the news.