Brexit chaos: Theresa May's government loses crucial vote once again on flagship Brexit deal The U.K. Parliament may now vote to request an extension to the Brexit deadline.

LONDON -- British Prime Minister Theresa May has suffered a huge setback after her Brexit deal was voted down by lawmakers for the second time in three months, even as the deadline for leaving the European Union approaches in less than three weeks.

The Brexit deal, which has received heavy criticism from all sides of British politics, was voted down by a margin of 149, with 242 in favor to 391 against, Tuesday night. In the end, it was a resounding defeat for the prime minister's flagship Brexit deal, which she has spent the best part of two years negotiating.

In January, May's deal was voted down by a majority of 230 votes. The final tally then was 432 against and 202 in favor of the deal, which is the biggest defeat for any legislation in the House of Commons' history.

After that, May went back to Brussels to renegotiate a better deal with EU leaders, despite the EU being consistently resolute in their position that the deal was not up for renegotiation.

But on Tuesday, it became clear that May had been unable to secure any major changes to the controversial "Irish Backstop" -- the provision that May's supporters said this was a necessary measure in order to avoid a hard border between Northern Ireland and the Republic of Ireland.

According to the critics of the deal, however, this would have kept the U.K. too closely aligned to the EU even after Brexit.

In substance, therefore, the deal on offer Tuesday was virtually the same as the one voted down by the U.K. Parliament in January.

Earlier Tuesday, May warned lawmakers that if they voted down her deal, "Brexit could be lost," implying that Britain could end up remaining in the European, despite voting to leave in the referendum of 2016.

The president of the European Commission, Jean-Claude Juncker, echoed those warnings Monday night, claiming that there would be "no third chance" in the negotiations and "it is this deal, or Brexit might not happen at all."

It looks increasingly likely that Brexit will be delayed. On Wednesday, lawmakers will vote on whether to leave the EU on the March 29 deadline with "no deal," which is unlikely given that most politicians believe it will be hugely damaging for the British economy.

If they vote against "no deal," another vote will take place on Thursday, where MPs will vote on whether to ask the EU to delay Brexit for the time being.

Losing the crunch vote represents a significant blow for the government's Brexit plans -- and could have significant implications for May's future as prime minister.

One lawmaker from May's own Conservative party told the BBC earlier Tuesday that if they lost the vote he could not see how the government could continue in office.

"I think there will have to be a general election," senior Member of Parliament Charles Walker said. "Because this parliament now looks very much like a failing parliament… I can’t see really how this government can continue in office [after losing]."