By promising to step down before 2022, the prime minister hoped to peel off MPs who fear she would be an electoral liability, but she also risked further undermining her already fragile authority.
Britain's ruling Conservatives have been divided for years over the European Union question, with younger MPs being largely in favour of leaving it, while older ones tended to be more supportive of it.
If the PM loses the vote, she would not be able to stand in the subsequent leadership contest.
The rebels shot their letters of no-confidence to the party's 1922 committee, which organises leadership contests.
May could be toppled if a simple majority of 317 Conservative MPs (members of parliament) vote against her, though a large rebellion could also leave her fatally weakened. Brady said the vote would be held in Parliament between 18.00 GMT and 20.00 GMT (11.30 pm and 1.30 am) on Wednesday, with the results announced soon after.
She did not say what she will do if, as many expect, there is an early United Kingdom election triggered by Britain's Brexit crisis.
The final two candidates are put to a vote of the full party membership across the country.
The ballot will be held in the House of Commons.
In a threat to the same Brexiteers who have driven the challenge against her, May said the tight deadline may force a new leader to delay or even cancel Brexit. "The prime minister must realize that, under all constitutional norms, she ought to go and see the queen urgently and resign". "So I very much doubt that parliament will vote for the deal, when it has the chance to do so", he said. At least 189 indicated public support for her and one bookmaker had the odds she would win at 89 percent.
Seeking Concessions May was informed of the challenge late on Tuesday, after returning from a tour of European capitals in an attempt to salvage her Brexit deal.
Speaking to BBC News, Ms Hewin said: "When the rumours emerged that there was going to be a leadership challenge or a confidence vote in the Prime Minister, we saw the pound falling quite dramatically last night".
But European Council president Donald Tusk warned the bloc would not reopen the agreement secured in November after months of negotiations, with Brexit looming on 29 March.
The last batch of letters came in after May - facing a heavy defeat - sparked fury among MPs by delayed a parliamentary vote scheduled for Tuesday on the Brexit deal she agreed with European Union leaders last month.
Both May and Tusk also said they would look at stepping up preparations for the potentially catastrophic possibility that Britain leaves the European Union without any new legal arrangements in place.
MP Graham Brady says the threshold of 48 letters from lawmakers needed to trigger a leadership vote has been reached.
The last batch came in after May delayed Tuesday's vote on the Brexit deal, a move that sparked outrage among MPs of all the political parties. Then it would fall to her successor to try to sort out Britain's Brexit mess.
Prospective leadership contenders are former foreign secretary Boris Johnson, former Brexit secretary Dominic Raab, home secretarySajid Javid, and worldwide development secretary Penny Mordaunt.
Guy Verhofstadt, the European Parliament's Brexit co-ordinator, expressed his disbelief at the political chaos engulfing Westminster.
Our technical teams will continue to monitor service performance closely over the next few days to ensure we remain stable. O2 has confirmed problems with mobile data across its network this morning (Thursday, December 6, 2018). ).
A new report claims illegal immigrants have been working for US President Donald Trump's luxury golf club in New Jersey. The article says that "New Jersey lawyer, Anibal Romero, who is representing them on immigration matters".
Kononenko arrived at the station Monday along with Canadian astronaut David Saint-Jacques and NASA astronaut Anne McClain. The others return home on December 20, leaving only three for Christmas dinner, not counting the mice and worms.
The chairman is the highest-ranking military officer in the country and serves as the principal military adviser to the President. US President Donald Trump walks across the South Lawn after returning to the White House in Washington, US, December 7, 2018.
But it's clear Epic Games isn't done surprising us with new content, keeping players coming back to see the next big thing. Naturally, a new season also brings with it a new Battle Pass (which has also received its own new trailer).
He was a popular teammates at stops with the Seattle Mariners , Cleveland Indians , Chicago Cubs , Astros and Angels . Castillo was a five-year veteran, representing the Pittsburgh Pirates , San Francisco Giants and the Houston Astros .
Kyler Murray transferred to Oklahoma after his freshman season, sat out a season per transfer rules and then backed up Mayfield. The O'Brien Award was initially given to the top player in the Southwest before going to a quarterback-only honor in 1981.
The low-frequency rumblings were collected by the InSight lander during its first week of operations at Mars. A version of the sounds was altered to be more perceptible to the human ears, according to Nasa.
He added that the Justice Department inspector general's investigation into these matters is looming over all of this. So far, more than 30 people have been charged or pleaded guilty in Mueller's investigation.
Dellavedova may not be Sexton's tutor, but as a sparring partner, his intensity will only make the 19-year-old Sexton better. The Cavs sent guard George Hill and a 2021 second-round selection to the Bucks, and forward Sam Dekker to the Wizards .
Ayers not taking job as White House chief of staff
President Trump broke the news himself, telling reporters about Kelly's exit as he left for the Army-Navy game on Saturday. It was Saturday afternoon that Trump confirmed the news before making his way to the Army-Navy game.
Spain braces for some 500 violent fans for Copa Libertadores
The victor of the Copa Libertadores will claim the last remaining place at the Fifa Club World Cup in the UAE later this month. Martinez ran the ball into the empty net and River's substitutes and staff all poured onto the pitch to begin the celebrations.