The SNP’s Westminster leader Ian Blackford has challenged both the Conservatives and Labour to back amendments to the EU Withdrawal Bill that would keep the UK in the customs union and see it stay part of the single market through membership of the EEA.
At Prime Minister’s Questions, Mr Blackford raised leaked government analysis suggesting a ‘Doomsday’ no-deal Brexit could clear supermarket shelves in Scotland.
"Will the Prime Minister stop her charade and vote for the Lords amendments next week for membership of the EEA and the customs union, protecting jobs and prosperity?" the SNP MP asked.
Mrs May said the Government is "committed" to ensuring there is no hard border between Northern Ireland and Ireland, wants to ensure as frictionless trade as possible with the EU and wants to be able to operate an independent trade policy.
"All of those are about ensuring that we protect jobs here in the United Kingdom," she said.
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He also asked if the Prime Minister understood the "catastrophic negotiating position she has cornered herself into".
Mr Blackford added that his query was the question Labour leader Jeremy Corbyn “should have asked” ahead of a crunch day-long debate on the Withdrawal Bill on Tuesday.
Both the Prime Minister and Mrs May face rebellions from MPs supporting single market membership through the EEA, with the Scottish Tory Paul Masterton putting his name to a new amendment backed by 12 other Conservative rebels.
In his own questions at PMQs, Mr Corbyn warned Theresa May's Brexit strategy is more chaotic than the rail timetable after he was pressed to rule out a second referendum.
The Labour leader likened the Government's European Union withdrawal approach to Northern trains, telling MPs the Prime Minister has "delivered more delays and more cancellations" than the franchise.
He also claimed Government "incompetence" threatens businesses and jobs as he sought to exploit Tory divisions over Brexit, against a backdrop of splits in his own party.
Mrs May simply replied "yes" when asked if she remains committed to leading the UK out of the EU by March 2019 and completing the transition period by December 2020.
Speaking at Prime Minister's Questions, she declined to be drawn on when the Government would publish its detailed post-Brexit vision in a white paper, but pressed Mr Corbyn on whether he wants a second referendum.
Mrs May also accused Labour of trying to "frustrate the Brexit process at every stage".
Mr Corbyn said: "When it comes to Brexit, this Government has delivered more delays and more cancellations than Northern rail.
"The Government's white paper is delayed, its customs proposals have been cancelled and it has ripped up its own timetable - just like our shambolic privatised railways. This Government's incompetence threatens our economy, businesses, jobs and our communities.
"So, my question to the Prime Minister is this: which will last longer, the Northern rail franchise or her premiership?"
Mrs May replied: "Labour voted for a referendum, they voted to trigger Article 50 and since then they have tried to frustrate the Brexit process at every stage."
She added: "Today we saw again they're refusing to rule out a second referendum.
"The British people voted to leave the European Union and it is this Government that is delivering on the vote of the British people."
Mrs May earlier stressed the importance of next week's votes on the Withdrawal Bill telling the Commons votes: "They will be important to show our commitment to do what the British people have asked us to do, which is to leave the European Union.
"If he's talking about clarity ahead of those votes, perhaps he'd take the opportunity of doing what he refused to do when I asked him last time in Prime Minister's Questions, which is to stand up and rule out a second referendum."
Mr Corbyn replied: "The last time I looked at the order paper it said 'Prime Minister's Question Time'."
He added the Government's post-Brexit vision is "nowhere to be seen".
When Mr Corbyn asked if the Government was favouring Brexit Secretary David Davis's proposal for a 10-mile buffer zone to deal with the Irish border, Mrs May replied: "We are looking at a number of, er, we're looking at the two options for the customs model.
"Both of those will do what we have committed to do, which is to ensure that we deliver no hard border in Northern Ireland and we've been very clear in the December joint report about what that means."