The Prime Minister will open five days of debate on her agreement with Brussels, knowing defeat in a crucial Commons vote next week will trigger a vote of confidence in her government, a possible challenge to her leadership within her party, and could send the UK crashing out of the EU and into an uncertain future.

Last night, the First Minister met privately with Mrs May and told her the vote on 11 December could not be a “false choice” between the proposed deal and a no-deal Brexit.

But the Prime Minister told Ms Sturgeon that the deal has the support of Scottish farmers, fishermen and business leaders, and challenged the SNP to vote for it or risk being responsible for a chaotic exit from the EU. Mrs May will today tell MPs that the public withdrew their consent for pooling sovereignty with the EU, and must have their wishes delivered through a Brexit deal.

Theresa May will have to defend her Brexit deal across five days of debate starting today. Picture: AFP PHOTO / PRU "HO/AFP/Getty Images

“Ultimately, membership of any union can only be sustained with the consent of the people,” the Prime Minister will say.

“In the referendum of 2016, the biggest democratic exercise in our history, the British public withdrew that consent. They confirmed that choice a year later by voting overwhelmingly for parties that committed to delivering Brexit.

“The referendum was a vote to bring our EU membership to an end and to create a new role for our country in the world.”

Mrs May will claim that only her deal can deliver an end to free movement of people while delivering “an unprecedented economic relationship that no other major economy has”.

“The British people want us to get on with a deal that honours the referendum,” the Prime Minister will say. “This is the deal that delivers for the British people.”

With around 100 Conservative MPs saying they could vote against the deal, the odds are stacked against the government. Labour has said it will bring a motion of no confidence in the government if it is defeated, which could bring about a general election. Mrs May’s DUP allies have hinted they could abandon her in the event of a confidence vote.

Opposition MPs are also set to push for a second EU referendum if the Brexit deal collapses.

Meeting Mrs May last night for the second time in two weeks, Ms Sturgeon appealed for a plan B and pledged to work with other parties to delay Brexit by extending Article 50 – something Downing Street ruled out yesterday.

Following the meeting in Mrs May’s Commons office, the First Minister insisted that next week’s vote “cannot – and must not – be a false choice between [the Prime Minister’s] proposed deal and a no-deal outcome, which threatens to be utterly disastrous.”

Ms Sturgeon added: “The SNP will lay our amendment to the meaningful vote later this week and we will continue to work with others to build consensus around alternative proposals that would deliver on the vote of the people of Scotland to remain.

“With the UK government’s own published figures now making clear that any kind of Brexit would make us all poorer, the time has come for all those who oppose the extreme Brexit championed by the right-wing of the Tory party to come together and make a stand.”

A Downing Street spokesman said: “The Prime Minister spoke about the support she has received from fishermen, farmers and business leaders – like Sir Ian Wood – who back the deal as it gives them the clarity and certainty they need to protect jobs and living standards.”

Over the coming days in the Commons, Mrs May will deploy senior Cabinet ministers to make the case, with Chancellor Philip Hammond, Foreign Secretary Jeremy Hunt and Home Secretary Sajid Javid expected to appear at the despatch box.

The first day of debate will be closed by Brexit Secretary Stephen Barclay, who faced embarrassment yesterday after appearing not to know when the UK is leaving the EU.

Giving evidence to MPs on the Brexit committee, Mr Barclay, who took over the role last month after the resignation of Dominic Raab, said Britain was quitting the bloc on 31 March, rather than the actual date of 29 March.

Tomorrow’s debate will focus on security, while Thursday’s debate will be on the economy.

Nicola Sturgeon pleads with Theresa May for Brexit plan B