However, he said the situation was unchanged if a deal that supersedes the backstop can not be reached "through no such demonstrable failure of either party". If that is defeated - the likely outcome - lawmakers will vote Thursday on whether to delay Brexit, something that needs to be approved by the European Union nations too. Does it want to hold a second referendum?
Ed Fulton, political trading spokesman for Sporting Index, said:"Theresa May has been to hell and back with Brexit, and it looks nearly certain that MPs will spurn her second deal, but she could have more on her side this time around".
While the majority of analysts seem confident that May's deal will once again be shot down, Alastair George, chief investment strategist at Edison, argued on Tuesday morning that the EU's overnight concessions might be enough to win over a significant amount of MPs. These had equal legal force with the withdrawal agreement, he claimed.
After analysing the assurances secured by Theresa May from her meeting with European Commission president Jean-Claude Juncker overnight and the advice offered by Attorney General Geoffrey Cox, the ERG's so-called "star chamber" of legal eagles said they did not feel it met the government's own standards.
Geoffrey Cox, the government's top lawyer, is due to give his opinion on Tuesday at 1230 GMT ahead of the vote due around 1900 GMT.
The motion put forward by the government said the joint instrument "reduces the risk" that the United Kingdom would be trapped in the backstop. It they vote yes then Brexit would take place with May's deal on or around 29 March. "However in our view sufficient progress has not been achieved at this time".More news: 70 million in path of 'bomb cyclone' across central US
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Brexit-supporting lawmakers in May's party had accused her of botching the negotiations with Brussels.
The backstop, an emergency fix aimed at avoiding controls on the sensitive border between the British province of Northern Ireland and European Union member Ireland, was the most contentious part of the deal Mrs May agreed to in November. This is what we can expect tonight.
Sterling also fell two cents against from £1.32 to £1.30 against the dollar.
"The prime minister has run down the clock and the clock has been run out on her", said Opposition Labour Party leader Jeremy Corbyn.
Others said it was now up to Snow to reply to the attorney general.
Pro-Brexit politicians in May's Tory party insist that the plan - known as the backstop - threatens to trap the United Kingdom inside the EU's trade regime forever, because it would be impossible for Britain to leave.
In the staunchly pro-Brexit port of Dover in southern England, retiree Mary Simpson said she felt her voice as a "leave" voter had not been heard.