David Mundell, as Scottish secretary, had threatened to resign if the province had a different relationship with the EU than the rest of the UK

Scottish Conservative MPs are expected to unanimously back Boris Johnson’s Brexit deal despite DUP claims that it risks the integrity of the Union.

David Mundell had threatened as Scottish secretary to resign from his post if an agreement led to Northern Ireland having a different relationship with the EU than the rest of the UK. He was sacked during the cabinet purge that followed Boris Johnson’s victory in the leadership contest in July.

Last night he said that he would back the prime minister’s proposals to create a border in the Irish Sea. His reversal provoked charges of hypocrisy from critics.

Privately some Scottish Conservatives admit that Nicola Sturgeon may seize on the Irish border solution as evidence of how an independent Scotland could operate