MPs voted against May's revised EU withdrawal agreement by 391 to 242 on Tuesday, another heavy defeat since January 15, when MPs rejected May's Brexit deal by a margin of 230, Xinhua news agency reported.

The voting started at around 1900 GMT, with the Prime Minister heading for a defeat.

A hoarse Prime Minister, who was carrying on her last-ditch battle to save her Brexit deal just hours before the crunch vote, failed to win over the ERG, a major faction within her Conservative Party.

The UK is scheduled to leave the European Union on March 29. May's Brexit deal was voted down on Jan 15 in the heaviest parliamentary defeat of any British Prime Minister in the modern era.

"I profoundly regret the decision this house has taken," May told lawmakers in a short speech right after the voting.

She added that the choices facing Britain were "unenviable", but because of the rejection of her deal. "They are choices that must be faced," she said.

May has secured legally binding changes to the deal on Monday night, but rebel lawmakers of her Conservative Party and those from the opposition Labour Party had said that these changes were not enough to persuade MPs to back the agreement reached by London and Brussels in November 2018 after years of painful negotiations.

"The reality is that nothing has changed," Jeremy Corbyn, the leader of Labour Party, said in the Parliament. "Nothing has changed. Not one single word was changed."

Corbyn said the Labour party put forward the idea of "remain and reform" in the referendum campaign.

With her Brexit deal rejected again in the UK Parliament, the Prime Minister then faces a possible defeat on a second vote on Wednesday to prevent a no-deal Brexit on March 29, and a third vote on Thursday to extend the Article 50 divorce process, likely until the end of June.