LONDON: Prime Minister Theresa May's Brexit deal faced a likely defeat in an historic parliamentary vote Tuesday that risked pitching Britain into the unknown just 17 days before its scheduled split from the European Union.
Parliament's failure to back the divorce terms could unleash economic chaos: it raises the danger of Britain severing ties with its biggest trade partner on March 29 without a deal after 46 years of EU membership.
A hoarse-sounding May warned lawmakers in a last attempt to sway them that "Brexit could be lost" if they voted against her and said a no-deal Brexit would deliver a "significant economic shock".
Last chance? Theresa May wins Brexit assurances from EU on eve of crucial vote
May had dashed off to Strasbourg on Monday to wrest concessions from EU leaders in a last-gasp bid to win parliament's blessing in one of its most consequential votes in generations.
The British leader announced that she had secured the "legally binding changes" to the vexing issue of the Irish border that lawmakers had long sought.
But Attorney General Geoffrey Cox said the risk in the most contentious points of the 585-page withdrawal deal agreed with the EU "remains unchanged".
May's initial agreement with Brussels was crushed in January by an unlikely alliance of pro-European and Brexit-backing MPs in January.
Members of the European Research Group (ERG) of Brexit hardliners in May's Conservative Party and the Democratic Unionist Party (DUP) that props up her minority government both came out against the deal on Tuesday.
The main opposition Labour Party also urged parliament to vote down May's plan, making defeat almost certain.
The pound reversed the gains it had made after May's announcement on Monday and tumbled after Cox's advice was released.
The so-called "backstop" solution for the Irish border -- designed to avert sectarian strife from returning to Britain's Northern Ireland -- is opposed by more fervent Brexit supporters.
They pressed May to secure the right for Britain to pull out of the arrangement or to make it time limited.
May seeks ‘push’ from EU on Brexit
But Brussels has called it essential for preserving the bloc's external border after Brexit.
The DUP said in a statement that "sufficient progress has not been achieved at this time" and called for a "sensible deal".
The DUP's consent was seen as vital for swaying members of May's own party to soften their opposition and either back the deal or abstain in the vote.
While a few said they had changed their mind as a result of her last-minute changes, there was scant evidence of a significant shift in Brexiteer support.
With just hours to go before the vote, May attempted to sway sceptics.
"I think everybody needs to recognise, for those who genuinely want to deliver Brexit, that actually if this deal does not go through tonight, then this house risks no Brexit at all," she said.
"The danger for those of us who want to deliver -- to have faith with the British public and deliver on their vote for Brexit -- is that if this vote is not passed tonight, if this deal is not passed, then Brexit could be lost," she said.
Leaders across Europe also united behind a message that this was the best and final offer Britain could expect.
"There will be no third chance," European Commission chief Jean-Claude Juncker said after his talks on Monday with May.
Another defeat would tee up additional votes on the way ahead that May has promised in a bid to preserve unity inside her fractured government.