Ballot opens for Tory MPs to cast votes on Theresa May's leadership

"Sterling has remained stable this morning despite a Conservative party leadership contest being triggered as Theresa May has vowed to contest the vote", said Michael Brown, senior analyst at Caxton FX in a statement to Yahoo Finance UK.

A leadership challenge is triggered if 48 Conservatives write letters demanding one to the chairman of the party's so-called 1922 committee, Graham Brady.

A ballot will be held between 1800 and 2000 GMT on Wednesday in a room at the House of Commons and an announcement made as soon as possible afterwards, he said.

But Brexiteers are demanding she entirely overhaul this contentious element of the proposal before trying again to put the deal to a vote in the House of Commons.

Brexit is Britain's most significant political and economic decision since World War II.

She said she was cancelling a trip to Ireland on Wednesday to remain in London, where she would lobby her Conservative colleagues to back her leadership.

Announcing the delay, May was laughed at by some lawmakers when she said there was broad support for the deal and that she had listened carefully to different views it - the result of 18 months of tortuous negotiations.

Supporters of Brexit say May's deal fails to deliver on the clean break with the bloc that they want.

Theresa May has told Conservative MPs she knows they will not let her lead them into another general election in 2022, though "in my heart" she would have liked to.

"That must start here in Westminster with politicians on all sides coming together and acting in the national interest".

In a defiant statement outside 10 Downing St., May said "a change of leadership in the Conservative Party now will put our country's future at risk".

The challenge to May "will be seen as self-indulgent and wrong".

Justice Secretary Gauke said that if MRs May lost, Brexit would have to be delayed.

The no-confidence vote will take place tonight, between 6pm and 8pm.

To survive the vote, May needs to get over half of the registered votes cast by the party's 315 MPs. Theresa May would need a simple majority of the total votes registered in order to win. If all elected lawmakers cast their ballots, that would now mean 158 votes.

Admitting likely defeat on Britain's potentially biggest political and economic shift since WWII, May was laughed at by some MPs when claiming broad support for key aspects of her deal reached with the European Union last month.

Yet senior colleagues of the Labour leader like Unite's Len McCluskey are vehemently opposed to another European Union referendum as they fear Labour support for one would lose the party significant support in Midlands and northern England seats.

She planned to address backbench lawmakers just before the leadership ballot opens.

What happens if Theresa May loses the vote of no confidence?

Conservative leadership contests have two parts.

"I have devoted myself unsparingly to these tasks ever since I became prime minister and I stand ready to finish the job".

The Conservatives had to build a "country that works for everyone" and deliver "the Brexit people voted for". The candidate with lowest number of votes drops out and voting continues until there are two contenders left.

The last time such a ballot took place was in 2005, when David Cameron and David Davis spent over a month competing for Conservative members' support, before Cameron was announced the victor.

May remains prime minister and party leader until a replacement is chosen.