Theresa May is facing a constitutional crisis after six opposition parties joined forces to accuse the government of contempt of Parliament over its failure to publish its full Brexit legal advice.
The Commons Speaker, John Bercow, said there was "an arguable case" that the government had committed contempt, after he was asked by Labour, the SNP, the Liberal Democrats, Plaid Cymru, the Green Party and the DUP to begin proceedings.
Earlier, Attorney general Geoffrey Cox admitted the UK could be locked into a customs backstop under the prime minister’s Brexit blueprint.
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Mr Cox confirmed that neither the UK nor EU would be able to unilaterally end the Northern Irish backstop arrangement if it came into force, in an address to MPs.
It also comes as The Independent’s petition calling for a Final Say referendum on Brexit was delivered to Downing Street, after more than a million people backed the campaign.
Editor Christian Broughton will be delivering one million Final Say signatures and People’s Vote spokesman Chuka Umunna MP will be delivering 300,000 People’s Vote signatures to Downing Street at midday.
Campaigners will be gathering outside the Churchill War Rooms from 11am before setting off for the prime minister's residence at 11.30am.
On Monday we will be heading to 10 Downing Street to deliver our petition calling for a Final Say on Brexit.
Well over a million of you have signed up, adding your names to our call for a full, public vote on the most important political question for a generation. It is time to make clear to the prime minister that the people want and need to be part of the Brexit process. One snapshot was not enough. Every signature counts so please continue to share the petition among your friends and family.
Only by giving people a Final Say on Brexit can we know with confidence how the country feels about our relationship with the EU.
Thank you for backing our call already. If you would like to show your support for our petition in person, meet us at the Churchill War Rooms near Parliament Square (at the bottom of the steps) at 10.30am on Monday 3rd December. And please share this petition – everyone should get the chance to back it.
Later today attorney general Geoffrey Cox is due to make a statement in parliament about his legal advice on the EU withdrawal agreement.
Theresa May is facing calls to make the opinion public. Labour said it is ready to combine with other opposition parties to start proceedings for contempt of parliament unless the report is published in full. Boris Johnson has described the prime minister's refusal to do so a "scandal".
Theresa May's top Brexit adviser has privately warned her that a key element of her exit blueprint would be a "bad outcome" for the UK.
Oliver Robbins, who led the behind-the-scenes talks with Brussels, reportedly told the prime minister that there was no legal guarantee that Britain could withdraw from the "backstop", which aims to prevent a hard border in Ireland if future trade talks fail.
Home secretary Sajid Javid has said that MPs are "very unlikely" to see plans for the UK's future immigration system before they vote on the Brexit deal.
Explaining the delay, the Home Secretary told BBC Radio 4's Today programme: "This is the biggest change in our immigration system in over four decades - the most significant change we're going to see in immigration as we take control of our immigration system, so it's important that we work on the details, that we listen to people, to businesses and others and we get the details right."
Mr Javid and chancellor Philip Hammond are reported to be pressing for the government to abandon the target of reducing net migration below 100,000 a year.
As parliament builds up to the vote on the EU withdrawal agreement on 11 December, Labour's shadow Brexit secretary has said it is inevitable that they will table a motion of no confidence in the government if the deal is voted down in the Commons.
Two Conservative MPs have backed calls for publication of the attorney general's legal opinion on the EU withdrawal agreement.
Simon Clarke MP and David Jones MP - both lawyers - pointed out that, although the advice is usually not divulged, there was a precedent for doing so in the advice of Lord Goldsmith to Tony Blair on the legality of the Iraq war.
Simon Clarke MP said: "We are about to embark on the most significant debate in parliament for many decades. The functioning of the backstop and our ability to ever leave it will lie at the heart of it, and the advice the attorney general has laid before the cabinet is crucial. There should not be two classes of MPs in this debate - those who are aware of the full ramifications and those who aren’t. The government accepted the will of the House that this advice would indeed be published. It would be an act of bad faith not to do so now - and one that would strengthen people’s suspicions that ministers refuse to do so for fear of how damning it is."
The Rt Hon David Jones MP said: "At this crucial moment in the Brexit process, it is essential that parliament should be as fully informed as possible on the legal issues surrounding the deal. These include, among others, the role of the European Court of Justice, the justiciability of the “best endeavours” provision and whether it is possible to withdraw from the backstop without the consent of the EU. I am sure that Geoffrey Cox has given sensible, dispassionate advice and the government is under a duty to ensure that the Commons sees it."
"Yes, it will be divisive and difficult. There are no easy ways out of this mess. But the people who gave the government the task of negotiating Brexit should have the Final Say on whether this is what they meant, and whether it’s what they want. If not, they should be entitled to say that we should stay, especially now we know for a fact, courtesy of the government itself, that all versions of Brexit leave us worse off."