BREAKING: Theresa May’s Brexit deal suffers another huge defeat

In a major rejection, British Prime Minister Theresa May’s Brexit withdrawal deal was voted down by lawmakers in the House of Commons.

MPs rejected the agreement by 391 votes to 242 -- a majority of 149.

It’s the second time her deal has failed.

The coming days will be unpredictable, as British lawmakers vote on whether to crash out of the European Union without a deal, or to delay the divorce process.

May had hoped that changes to her deal agreed with the EU at the last minute on Monday night would get her deal across the line, but many lawmakers remained reluctant to back it.

British lawmakers are tweeting that the "no" lobby -- where MPs are voting on Theresa May's Brexit deal -- is "absolutely rammed."

"Haven't seen the no lobby this full since the last meaningful vote," Tim Farron from the Liberal Democrats wrote.

British MPs are now voting on Prime Minister Theresa May’s Brexit deal for the second time, almost two months after it suffered the largest ever Commons defeat. The result of the vote is expected imminently.

Conservative lawmakers continue admit that while Theresa May's deal isn't perfect, they have chosen to support it.

Edward Leigh appealed to MPs in the House of Commons that if they reject the Prime Minister's deal, they are going against the "will of the people" who voted to leave the EU on March 29.

"There is a much greater risk for us Brexiteers that parliament will block a no deal and the next day parliament will vote to extend article 50. For those of us who believe in Brexit and delivering the will of the people, that is a far greater risk -- a far greater risk -- than the fairly small risk of us being trapped in a backstop forever.

"So I appeal to my fellow Brexiteers -- you may not like the deal, it's not perfect, but it delivers Brexit and let's go for it."

While another Conservative MP, Tracey Crouch said she would support May's deal "only to stop remainers from keeping us locked in the EU forever."

The European Union's chief Brexit negotiator, Michel Barnier, has warned UK lawmakers that without a withdrawal agreement, Britain will crash out of the EU on March 29.

"Let me be clear: the only legal basis for a transition is the WA. No withdrawal agreement means no transition," he tweeted.

The crunch Brexit vote is due to happen in the next 30 minutes. Here's what you'll see if you're watching the action in the House of Commons at 7 p.m. UK time (3 p.m. ET):

The Speaker of the House of Commons, John Bercow, will say something along the lines of: "The Question is, that the Bill be read a second time. As many as are of that opinion say Aye."

At this point, those who support the bill yell "Aye!" He then adds: "of the contrary No," prompting those who are against it to shout "No!"

Bercow then says "I think the Ayes have it..." If MPs yell "No!" in response, he will announce a vote by bellowing: "Clear the Lobbies". 

The division bell will then sound throughout the Houses of Parliament.

MPs will file out of the Commons to cast their vote by coming back into the chamber again, through one of the two division lobbies, the "Aye" lobby (to vote yes) or the "No" lobby, past clerks, who take their names, and tellers, who count up the votes.

They will have eight minutes to do this; once they are back inside, the doors are locked and the tellers announce the numbers of "Ayes to the left" and "Noes to the right."

The Speaker will then repeat the numbers, and announce which side has won, either: "the Ayes have it," or "the Noes have it," before instructing the Parliamentary authorities to "Unlock the doors!"

Mary Lou McDonald, Sinn Fein president, told CNN's Christiane Amanpour that Ireland has a "very unique set of circumstances. It was always the case, therefore, that a set of unique bespoke solutions would have to be offered for our island to protect our economy, our trade, our citizens, our rights, and crucially our peace process."

The Brexit negotiation process, McDonald said, has been "marked by recklessness on the part of the Tory government."

McDonald went on to say that, "Brexit has laid bare for all to see the real jeopardy that partition brings to the island of Ireland: to our economy, to our society, to our social fabric and to our institutions."

"The fact is that the border on the island of Ireland is now no longer simply an Irish problem: it is now a European problem."

Should the UK crash out of the European Union, McDonald said, "a referendum on Irish unity, I think, will be absolutely essential."

Independent Group MP Joan Ryan has set out the breakaway group's plans while speaking to CNN's Hala Gorani. Tomorrow, the group will vote against a no deal Brexit -- "that should be off the table," Ryan said. Today, she added, they would vote against May's deal.

On Thursday, the Independent Group will press for an extension of Article 50, Ryan said, adding, "We want that extension of Article 50, and we want a series of indicative votes to decide which withdrawal deal to put to the people."

"We should go back to the people for a choice between the status quo -- remain -- or the withdrawal deal that gets the majority vote next week," she said.

Britain's former Foreign Secretary Boris Johnson has lambasted the efforts of Prime Minister Theresa May and Attorney General Geoffrey Cox to disguise the "embarrassment" of their Brexit deal, saying "whatever the government has tried to do, it has not, I'm afraid, succeeded," according to the UK's Press Association.

"The result is like Adam and Eve in the Garden of Eden -- they have sewed an apron of fig leaves that does nothing to conceal the embarrassment and indignity of the UK," Johnson told the House of Commons.

"We can ... decide that if the EU is unwilling to accept the minor changes that we propose that we'll leave without a deal -- and, yes, I accept that that is in the short term the more difficult road -- but in the end it's the only safe route out of the abyss and the only safe path to self respect."