Theresa May's Brexit deal will face fresh scrutiny when the Cabinet's full legal advice is published, following one of the most punishing days in the Commons for a sitting Government in recent memory.
Allies of the prime minister have looked at the potential for a People's Vote which would be between remaining in the European Union or her deal, which they believe could be won if there is a uarantee to end freedom of movement.
May said she was speaking to MPs about giving parliament a bigger role in whether the Northern Irish backstop arrangement would be triggered, though she gave few details.
On Tuesday, just hours before the start of a five-day debate in the British Parliament on May's Brexit deal, a top law official at the European Court of Justice (ECJ) said Britain could pull back its formal divorce notice.
The Times newspaper reported that senior ministers were urging May to delay it for fear of a rout.
"First of all because in that backstop we will be making no financial obligation to the European Union; we will not be accepting free movement; and there will be very light-touch level-playing field requirements", she said.
Mrs May is reportedly dead set on delivering the result of the 2016 referendum and "loses her temper and raises her voice" when the prospect of a re-run of the vote is raised.
No 10 has said the Commons vote will go ahead on Tuesday, despite claims it could be delayed to avoid defeat.
Under the arrangements, "for regulatory purposes, GB is essentially treated as a third country by NI for goods passing from GB into NI", he said.More news: New Series, Old Mistakes: India's Top-order Collapses at Adelaide
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"In the implementation period, we still have to negotiate the terms, but there will be concerns about the fact that they would require, I'm sure they would require, some more money to be paid, for example".
May said some in parliament were trying to frustrate Brexit and that she did not think another referendum on Brexit was the right course.
"She either has to go back to Brussels and say no to the backstop or it's no deal".
It is likely to be seized upon by Tory critics of Mrs May's deal, who argue that the backstop arrangement to keep the Irish border open will deny the United Kingdom the power to withdraw from a customs union without agreement from Brussels.
Concerns about the backstop are a key driver of opposition to the deal among both May's own Conservative lawmakers and the Northern Irish Democratic Unionist Party (DUP), which props up her minority government.
Mr Javid warned that "no matter how effectively" the government prepares for a no-deal Brexit, there would be "consequences" for the UK's security.
"Despite statements in the Protocol that it is not meant to be permanent and the clear intention of the parties that it should be replaced by alternative, permanent arrangements, in global law the Protocol would endure indefinitely until a superseding agreement took its place", the advice said.
She said it would not be in the "national interest" to block the Withdrawal Agreement, adding: "The only certainty would be uncertainty".