The Scottish Secretary claimed he is surprised the SNP have not proposed building a wall to separate England and Scotland, given recent border talk.

Alister Jack made the remark as he criticised comments from Emma Harper, an MSP in the last parliament who is standing for the SNP in West Dumfries and Galloway.

Ms Harper suggested erecting “the softest of borders” with England could create jobs in an independent Scotland, also noting “we can show that a border will work” when questioned about it during a television interview.

But UK Cabinet minister Mr Jack told the House of Commons: “I would note with some astonishment the comments of the South of Scotland MSP Emma Harper that a border would be a good way of creating jobs, despite the fact that 60% of our trade is with the rest of the UK.

“All I would say is that if the SNP think a border is such a good idea for jobs, I’m surprised they don’t want to go the whole hog and propose building a wall.”

An SNP spokesman, responding to the interview with Ms Harper, last week said independence is about “getting rid of governments that Scotland doesn’t vote for – not putting up barriers”.