THE SNP has challenged David Mundell to rule out serving in a no-deal cabinet after warning Boris Johnson that such a Brexit would be welcomed by Nicola Sturgeon with “unseemly glee” and “damage our economy”.

The call comes after the Scotland Secretary issued a thinly veiled warning to Johnson in the Observer – despite saying he had not ruled out serving in the former foreign secretary’s cabinet.

Mundell told Johnson “protecting our Union must be our top priority”, and that her successor must deliver “a Brexit that works for the whole UK, including Remain-voting Scotland”.

He added: “Scotland has a first minister whose only true priority is the pursuit of independence. She poses as a defender of devolution while seeking to destroy it. She seizes on the problems of leaving the EU with unseemly glee. But it is easy to see why.

“A difficult no-deal Brexit would not only damage our economy, it would fuel nationalist claims of a UK that is insensitive to Scotland’s needs. The new prime minister faces considerable challenges, and the future of the UK is high on the list.”

Edinburgh East MP Tommy Sheppard says Mundell must now pledge not to help deliver a Brexit that could cost Scottish jobs and harm the health service, which “will be a disaster for Scotland”.

But last night the Scotland Office told The National that the SNP was running scared of the Scotland Secretary.

A source said: “The SNP voted against the Brexit deal three times. The truth is, they want us to leave the EU without a deal because they believe it would help their campaign for independence.

“No wonder Nicola Sturgeon is desperate to get rid of a Secretary of State for Scotland who will fight to leave the EU with a Brexit deal and continue to oppose her demands for a second independence referendum. The new PM will choose the cabinet, not the SNP.”

Sheppard said Mundell must “categorically rule out serving in a

no-deal Tory cabinet”.

He added: “David Mundell is well aware that a no-deal exit from the EU will be a disaster for Scotland and in his own words it will ‘damage our economy.’ His previous threats to resign have all proven to be nothing more than hollow words – but he must now go beyond a simple newspaper column and categorically rule out serving in a no-deal Tory cabinet. With both Tory candidates ramping up talk of a no-deal Brexit, the Secretary of State for Scotland for once must take a principled stand and make clear that he would not serve in a Tory government that would inflict that policy upon Scotland, which we know will cost up to 100,000 jobs across Scotland and hit people’s living standards – including in David Mundell’s own constituency.

“Beyond the hollow rhetoric of both Jeremy Hunt and Boris Johnson about preserving the Union, it’s clear that they would both ignore Scotland’s people and its democratic vote – as has been the case for the past three years – so that they can push ahead with their catastrophic Brexit plans. Any pretence that Scotland will ever be treated as an equal partner in the UK has long gone.”

Johnson and fellow PM candidate Jeremy Hunt have suggested they would be willing to back a no-deal Brexit. Last month Mundell drew criticism after he told ITV Border he had “never said” he would refuse to serve under Boris Johnson – despite previously saying the former London mayor is “only focused on his own self-interest” and: “Mr Johnson and I don’t agree on a whole range of issues and I don’t see myself being able to serve in that way.”

But in the much-mocked exchange, Mundell told the channel he has “never explicitly ruled out” a job in a Johnson-led cabinet.