MPs are set for a crunch vote on the Prime Minister's Brexit deal as they enter into the final day of Commons debate.

Theresa May is widely tipped to lose the meaningful vote on the withdrawal deal her government struck with EU, expected between 8pm and 9pm on Tuesday.

She has warned MPs that rejecting her deal would be "the height of recklessness" and could lead a no-deal or no-Brexit outcome.

But dozens of parliamentarians from her own party are expected to vote it down, along with MPs from Labour, the SNP, the Liberal Democrats and even the DUP, which props up May's minority government.

Opening for the government in Tuesday's debate, attorney general Geoffrey Cox warned the Commons it faces a choice between order with May's deal and chaos if it is defeated.

Cox, the chief legal adviser to UK ministers, said MPs risk being viewed as "children in the playground" if they create legal uncertainty by rejecting the agreement.

He added: "We are playing with people's lives."

The Prime Minister will close the debate with a speech to Parliament before 7pm.

If she loses the vote as anticipated, Labour has indicated it will quickly move to force a confidence vote in her government.

If it falls, Jeremy Corbyn's party wants to hold and win a general election and renegotiate the Brexit deal.

He has also indicated his party could choose to extend Article 50 if it entered government, giving Britain more time before leaving the EU than its current deadline of March 29.

Remain-supporting parties such as the SNP and Lib Dems are calling for a second EU referendum, or so-called People's Vote, if May's deal is defeated.

Speaking earlier on Tuesday, the SNP's Westminster leader Ian Blackford called for Article 50 to be "paused" and pointed to UK and Scottish government analysis that all forms of Brexit would leave the country worse-off.

He added: "We have to say to people 'is that really what you want?'. Do you want to diminish your living standards? Because that will happen.

"We've already seen the impact that we've had post-referendum. Sterling fell, inflation went up, food prices went up.

"We're all paying a price for what happened in 2016 - let's not double the damage by going ahead with this."

Blackford said the Prime Minister's deal "doesn't work" and urged all MPs to reject it.

On the Brexiteer side, many Tory backbenchers and DUP MPs are opposed to the withdrawal agreement's proposals for a backstop solution to the Irish border question.

This would see the UK enter into a temporary customs arrangement with the EU beyond 2020 to ensure border checks are not needed between Northern Ireland and the Republic of Ireland.

Under the backstop, Northern Ireland would also follow EU regulatory rules set down by the single market for goods, differentiating its arrangements from the rest of the UK, a scenario the DUP refuses to endorse.

The backstop would only come into effect if the UK and the EU are unable to complete a free trade agreement before the end of the transition period on December 31, 2020.