The ‘Common Market 2.0’ proposal put forward by Conservative backbencher Nick Boles is modelled on Norway’s close relationship with the EU, with the added requirement of a close customs relationship that includes frictionless trade for agricultural and food products.
The SNP came under pressure over the weekend after abstaining on the Boles plan last week, despite the Scottish Government previously calling for the UK to stay in the single market and customs union as the least damaging Brexit option.
SNP Westminster leader Ian Blackford said on Monday morning: “The key thing for us is that we stay in the EU, we want to revoke Article 50, we want to put [the Brexit deal] back to the people in a People’s Vote, but we will be prepared to compromise on the basis of protecting jobs, staying in the single market and customs union - so we will vote for the Boles amendment.”
In a post on twitter, Nicola Sturgeon said: "[It's] really important to remember that tonight’s votes are not on a preferential basis - an SNP vote for [the single market and customs union] would only be to keep that option alive in case it later becomes only alternative to a harder Brexit. Our preference is stopping Brexit."
Labour also announced it would whip its MPs to vote for the Common Market 2.0 plan, after only issuing a recommendation to do so last week.
It promises to deepen the split between the party leadership and MPs representing Leave-voting areas, who argue that Labour should stick to its manifesto commitment in 2017 to end free movement.
A party spokesman said: “In line with our policy, we're supporting motions to keep options on the table to prevent a damaging Tory deal or no deal, build consensus across the House to break the deadlock and deliver an outcome that can work for the whole country.”
Common Market 2.0 emerged as the third most popular option after falling by 94 votes. A proposal from Tory MP Ken Clarke for the UK to remain in the customs union but not the single market was the most popular, falling by just six votes, while a motion calling for any plan to be put to a referendum was defeated by 27 votes.
Downing Street raised the stakes in the race to become the most popular soft Brexit alternative, indicating that it will seek to put the winner up against the Prime Minister’s Brexit deal in a runoff vote on Wednesday - but only if it believes Theresa May’s deal can win.