The Prime Minister warned this morning that if MPs refused to back her EU exit deal it would push the UK into “uncharted territory”.
What that territory would look like remains to be seen however as each MP has a different view on what would happen.
Mrs May cautioned that binning her deal could result in “no Brexit at all”, while Cabinet colleague Dr Liam Fox said the opposite and argued blocking the PMs deal would see a “no deal” Brexit with all the ramifications for jobs and trade.
MPs were due to vote on the deal in December, but with flagging support the Government pulled the vote in a bid to give more reassurances to doubters over the festive period.
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Debate will resume on Wednesday and the vote is officially slated for the week of January 14, but MPs look no closer to reaching agreement.
So, what are the sticking points?
A major point of contention has been the Northern Ireland Brexit backstop which forms part of Mrs Mays exit plan.
The backstop is effectively an insurance arrangement required by the EU and would see the UK enter into a temporary customs union with the EU if a future trade deal was not agreed during the transition period which will run until 2020.
According to its critics, there are two main problems with the backstop. The first is that the UK would not be able to unilaterally exit the mechanism without the EU's approval, leading some to fear Brussels could trap the UK.
A second issue is that the wording of the backstop means technically it could be indefinite, the withdrawal agreement says only that the provisions apply "unless and until they are superseded, in whole or in part, by a subsequent agreement".
RETURN: MPs will return to Parliament this week to consider the PM's Brexit plan (Pic: GETTY)
Mrs May has consistently said that the backstop, if it comes in at all, would only be temporary and has insisted the UK and EU will reach an agreement over future trade in the transition period.
Aside from the backstop MPs on both ends of the EU spectrum, whether hardline Brexiteer or Remainer, say the deal is too much of a “halfway house” and is either too close to the EU or too far removed economically.
The Prime Minister has said that no alternative plan is able to respect the 2016 referendum result, protect jobs and provide certainty to citizens and businesses.
Addressing opponents on both the Remain and Brexiteer wings of the Commons, she said: "There are some in Parliament who, despite voting in favour of holding the referendum, voting in favour of triggering Article 50 and standing on manifestos committed to delivering Brexit, now want to stop us leaving by holding another referendum.
"Others across the House of Commons are so focused on their particular vision of Brexit that they risk making a perfect ideal the enemy of a good deal.
"Both groups are motivated by what they think is best for the country, but both must realise the risks they are running with our democracy and the livelihoods of our constituents."