UK Prime Minister Theresa May has announced her resignation today after pressure on her to quit reached a critical point following her failure to win support for her Brexit deal.

The Conservative leader broke down in tears as she said she would stand down as Tory party leader on June 7 and make way for a successor.

"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," said Mrs May.

"So I am today announcing that I will resign as leader of the Conservative and Unionist Party on Friday the 7th of June."

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Her voice breaking, Mrs May said she would be leaving a job it has been "the honour of my life to hold."

Her announcement came after she met with the chairman of the party's key backbench committee in London on Friday morning, local time.

The 1922 Committee set the showdown meeting for Mrs May, who agreed to set a departure timetable rather than face a leadership challenge.

Mrs May has repeatedly failed to win the UK Parliament's approval for a European Union divorce deal, and this week she faced a mutiny when a senior minister quit and Cabinet colleagues expressed doubts her latest bill would pass.

Several British media outlets reported that Mrs May would agree to give up the prime minister's post on June 10, sparking a Conservative leadership contest. She may then stay in office as a caretaker prime minister until Tory MPs and members choose a successor.

The humiliating spectacle of the prime minister detailing her departure date follows a toxic response to her latest Brexit plan this week from cabinet colleagues and Conservative MPs.

Britain's Prime Minister Theresa May arrives to make a statement. Photo / AP
Britain's Prime Minister Theresa May arrives to make a statement. Photo / AP

Mrs May has previously said she would step aside once a Brexit deal had been passed by parliament, and launched a fresh bid on Tuesday for politicians to vote on a revised bill in early June. The government has now postponed that vote.

MPs have already overwhelmingly rejected her EU divorce plan, agreed with European leaders last year, three times.

Her latest proposals, which included giving them the option of choosing to hold a second referendum on Brexit to agree a deal, prompted a furious reaction among Conservatives.

British Prime Minister Theresa May reacts as she makes a speech in the street outside 10 Downing Street. Photo / AP
British Prime Minister Theresa May reacts as she makes a speech in the street outside 10 Downing Street. Photo / AP

Pressure intensified on Mrs May after Andrea Leadsom — one of cabinet's strongest Brexit backers — resigned on Wednesday from her post as the government's representative in parliament.

In her resignation letter, Ms Leadsom told the prime minister she no longer believed that her approach would deliver on the 2016 referendum result to leave the EU.

After months of political paralysis over Brexit, the clamour for the PM to stand down has been growing, and intensified after disastrous results in the May 2 English local elections.

In this October 3 , 2018 file photo Conservative Party Leader and Prime Minister Theresa May dances as she arrives on stage. Photo / AP
In this October 3 , 2018 file photo Conservative Party Leader and Prime Minister Theresa May dances as she arrives on stage. Photo / AP

The Conservatives are expected to fare similarly badly in this week's European Parliament elections when the results are announced late Sunday, when they are projected to come fifth, behind the Green Party.

The leadership battle could take about six weeks, during which time Mrs May may try to pass some of the less controversial parts of her Brexit deal. She is also set to meet with Donald Trump during his state visit to the UK from June 3-5.

In this July 13, 2016 file photo Queen Elizabeth II welcomes Theresa May, left, at the start of an audience in Buckingham Palace, London. Photo / AP
In this July 13, 2016 file photo Queen Elizabeth II welcomes Theresa May, left, at the start of an audience in Buckingham Palace, London. Photo / AP

Many of Mrs May's former allies have now turned against her, with foreign secretary Jeremy Hunt urging her to give up on her efforts to pass her Brexit legislation, The Times reported. Home secretary Sajid Javid also told her that her bid for a second referendum was doomed.

Timeline of Brexit and events leading to May's departure

A timeline of key events in how Brexit unfolded and how the political crisis led up to Theresa May's ouster as British prime minister:

May 7, 2015: British voters elect a majority Conservative government. Then-Prime Minister David Cameron confirms in his victory speech that there will be an "in/out" referendum on Britain's EU membership.

Feb. 20, 2016: Cameron confirms that he will campaign for Britain to remain in the 28-nation bloc. The referendum date is set for June.

June 23, 2016: Britain votes 52 per cent to 48 per cent to leave the EU.

June 24, 2016: Cameron says he will resign in light of the results.

US President Donald Trump, left, listens to British Prime Minister Theresa May, right, speak in 2018. Photo / AP
US President Donald Trump, left, listens to British Prime Minister Theresa May, right, speak in 2018. Photo / AP

July 13, 2016: Following a Conservative Party leadership contest, May, then Home Secretary, becomes prime minister.

Oct. 2, 2016: May says that Britain will begin the formal process of leaving the EU by the end of March 2017. In order to do this, the British government would have to invoke Article 50 of the EU's Lisbon Treaty.

March 29, 2017: The British government formally triggers Article 50, setting in motion a plan for Britain to leave the EU on March 29, 2019.

June 8, 2017: A general election called by May to bolster her party's numbers in Parliament to help with the Brexit negotiations backfires as her Conservative Party loses its majority and continues in a weakened state as a minority government.

An effigy of British Prime Minister Theresa May passes by Downing Street during a Peoples Vote anti-Brexit march in London. Photo / AP
An effigy of British Prime Minister Theresa May passes by Downing Street during a Peoples Vote anti-Brexit march in London. Photo / AP

July 7, 2018: May and her Cabinet endorse the so-called Chequers Plan worked out at a fractious session at the prime minister's country retreat. It leads to the resignations of Brexit Secretary David Davis, Foreign Secretary Boris Johnson and others who favor a more complete break with the EU.

November 25, 2018: EU leaders approve a withdrawal deal reached with Britain after months of difficult negotiations. May urges British Parliament to do the same.

December 10, 2018: May delays the planned Brexit vote in Parliament one day before it is to be held because it faces certain defeat. She seeks further concessions from the EU.

December 12, 2018: Conservative lawmakers who back a clean break from the EU trigger a no-confidence vote in May over her handling of Brexit. She wins by 200 votes to 117, making her safe from another such challenge for a year.

May waits for the arrival of European Council President Donald Tusk. Photo / AP
May waits for the arrival of European Council President Donald Tusk. Photo / AP

January 15, 2019: The Brexit deal comes back to Parliament, where it is overwhelmingly defeated in a 432-202 vote.

March 12, 2019: Lawmakers reject deal again.

March 23, 2019: Anti-Brexit protesters flood a central London by the hundreds of thousands demanding a new referendum on whether to leave the EU.

March 28, 2019: May offers up her job in exchange for her Brexit deal, telling colleagues she would quit within weeks if the agreement was passed.

March 30, 2019: British lawmakers reject the government's Brexit deal for a third time.

Britain's Prime Minister Theresa May makes a statement outside 10 Downing Street in London. Photo / AP
Britain's Prime Minister Theresa May makes a statement outside 10 Downing Street in London. Photo / AP

April 11, 2019: Britain and the EU agree to extend the Brexit deadline to Halloween. The Oct. 31 cutoff date averts a precipitous Brexit on April 12.

May 7, 2019: The UK government acknowledges for the first time that the country will definitely take part in the European Parliament elections because there's no chance that a Brexit deal can be approved in time to avoid them

May 17, 2019: Talks between Britain's Conservative government and the opposition Labour Party seeking a compromise over Brexit break down without agreement plunging the country back into a morass of Brexit uncertainty.

May 21, 2019: May offers a concession to lawmakers, giving them the chance to vote on whether to hold a new referendum on the country's membership in the EU — but only if they back her thrice-rejected Brexit agreement.

May 24, 2019: May says she will step down as Conservative Party leader on June 7 and will serve as caretaker prime minister until her successor is chosen.

- AP