Downing Street has warned that a revolt by Tory Brexiteers could “seriously damage” the prime minister’s attempts to get a revised Brexit deal.
MPs will vote on the next steps in the process later but BBC political editor Laura Kuenssberg says some Tories are refusing to back the government.
They say the government’s motion would rule out a no-deal Brexit and undermine the UK negotiating position.
But Liam Fox warned MPs against sending the “wrong signal” to Brussels.
The international trade secretary, who campaigned for Leave in the 2016 referendum, told the BBC: “This is not an academic debate. It’s listened to quite seriously by those who will be negotiating with the UK.”
The prime minister has asked MPs to approve a motion simply acknowledging that the Brexit process was ongoing and restating their support for the approach.
However, some Tory backbenchers are angry that it combines the view backed by a majority of MPs last month that the government should seek an alternative to the “backstop” – the “insurance policy” aimed at avoiding a return to border checks between Northern Ireland and the Irish Republic – with a separate move to stop Brexit happening without a formal deal.
Downing Street has ruled out compromising over what they describe as an “anodyne” motion.
It says if “parts of the ERG” [the influential Brexiteer European Research Group] vote against motion, the government expects to be defeated and argues the EU will conclude that Theresa May cannot command a stable majority and there is no point making further concessions in negotiations.
Backbench Tory Brexiteer Bernard Jenkin said he had not yet decided how to vote but described the government motion as “gratuitously divisive”.
He told the BBC: “It would have been much better if they’d consulted the 100 or so MPs that represent the majority of their backbenchers before tabling this motion.”
The UK is due to leave the EU on 29 March, whether or not a deal has been approved by the Commons.
Mrs May is continuing to try to get a Brexit deal through Parliament, after MPs rejected it by a historic margin in January. The prime minister says she is seeking legally-binding changes to the controversial “backstop”.
No 10 insists Mrs May still plans to hold a vote on a deal as soon as possible but Labour has accused her of “running down the clock” in an effort to “blackmail” MPs into backing her deal.
Several MPs have tabled amendments – which set out alternative plans – including one from Labour that would force the government to come back to Parliament by the end of the month to hold a substantive Commons vote on its Brexit plan.
Another, from the SNP, calls on the government to pass a law leading to the Brexit process being halted.
Commons Speaker John Bercow is yet to decide which of these will be considered by MPs.
Meanwhile, 43 former British ambassadors and high commissioners have called on the prime minister to extend the Brexit deadline.
In a joint letter published on Thursday, they argue the UK should not leave the EU without more clarity about the future relationship with the bloc, adding that the current “Brexit fiasco” makes a “powerful argument” for another referendum.
Could Brexit cause a Labour split?
You’ll be used to people in my kind of job saying things like, “these are critical days”.
And hands up, on many of the occasions when a big move is predicted, a damp squib often comes along to squelch the expectation.
What I’m about to say may well be a repetition of that familiar phenomenon. But I’m not the only person in Westminster this week to be wondering whether after many, many, many months of private conversations where this possibility was discussed, in the next couple of weeks, maybe even in the next couple of days, something that actually is critical is going to start happening.
What happens next?
The prime minister has promised to return to the Commons on 26 February with a further statement – triggering another debate and votes the following day – if a deal has not been secured by that date.
If a deal is agreed, MPs will have a second “meaningful vote”, more than a month after Mrs May’s deal was rejected in the first one.
The EU has continued to say it will not renegotiate the withdrawal agreement.
On Wednesday, European Council President Donald Tusk tweeted that “no news is not always good news”, saying the EU was “still waiting for concrete, realistic proposals from London”.
The prime minister has also said she will lift the requirement for a 21-day period before any vote to approve an international treaty, which means she could delay the final Brexit vote until days before the UK is due to leave the EU.
Former attorney general Dominic Grieve warned on Tuesday that time was running short for the ratification of a deal under the Constitutional Reform and Governance Act.
The Act requires 21 sitting days before the ratification of any international treaty, to allow MPs to study the agreement.
But Mrs May responded: “In this instance MPs will already have debated and approved the agreement as part of the meaningful vote.”
If there was not time for normal procedures, the government would amend the law around Brexit to allow it to be ratified more quickly.