Theresa May is facing a revolt by Brexit-backing ministers as the Cabinet meets at Chequers to finally sign off the government's approach to quitting the EU.
Up to seven members of her top team – including Boris Johnson, David Davis and Michael Gove - could formally reject Number 10's plan for breaking the deadlock in the government’s EU negotiations.
They are angry at Mrs May's proposal to effectively keep Britain in the single market for goods, but not for services.
The plan would also see "harmonisation" of regulations between Britain and the EU in an attempt to maintain an open border between Northern Ireland and the Republic of Ireland - but potentially scuppering the chances of a free trade deal between the UK and America.
The rebel ministers, who also include Leave supporters like Penny Mordaunt and Andrea Leadsom, held crunch talks at the Foreign Office last night to discuss their response to Mrs May's proposal.
It is thought that they could present their own vision of a harder Brexit based on the deal struck between the EU and Canada at today's meeting, which is scheduled to last from 9.30am until 10pm.
May herself said the Cabinet had a "duty" to agree a united Brexit approach, which will be published in a white paper later this month.
In a statement issued ahead of the Chequers summit, she said: "Now is the time for another step forward. We want a deal that allows us to deliver the benefits of Brexit – taking control of our borders, laws and money and by signing ambitious new trade deals with countries like the US, Australia and New Zealand.
"This is about agreeing an approach that delivers decisively on the verdict of the British people – an approach that is in the best interests of the UK and the EU, and crucially, one that commands the support of the public and Parliament."
It has been reported that the May has brought civil servants to Chequers who will update the Brexit paper as differences between ministers are resolved.