DAVID Mundell has insisted it would be “incredible” for Holyrood to refuse to back Westminster legislating for Scotland on Brexit as it would lead to fewer powers returning to Edinburgh from Brussels.

The Scottish secretary said he was “very relaxed” about the process involving a so-called Legislative Consent Motion[LCM], declaring: “We’re going to seek it.”

Earlier, the SNP leadership made clear that it believed Holyrood had the power to block Theresa May’s Brexit legislation by refusing to grant an LCM and suggested it would demand, as the price for not doing so, a seat at the Brexit negotiations in Brussels.

An LCM is the parliamentary means by which MSPs agree that Westminster can legislate on what are normally devolved matters.

Ian Blackford, the SNP leader at Westminster, said: “We certainly know this morning it is the case the Government is going to have to come to Edinburgh in order to get through an LCM."

He emphasised how his party’s approach would be one of seeking “compromise” rather than confrontation with the Conservative Government.

The Highland MP explained: "Of course, it is right - and many people have said this - that the Scottish Government should be represented at the talks in Brussels.

"For us, it is about maintaining our ability to trade through the European single market, to have the benefit of the customs union and, as a consequence of that, free movement of people," said Mr Blackford.

But asked if the Prime Minister was not compliant with such demands, he suggested Nicola Sturgeon’s administration could threaten action.

“Whatever you do in a situation like that is you don’t show your hand because it’s about negotiating the best deal for the people of Scotland.”

Asked if Holyrood could, therefore, try to block the Repeal Bill, Mr Blackford replied: "Of course, that is there. But I am not talking about that. I am talking about the spirit of compromise. I am hoping that we can get some sense and a recognition that our interests are perhaps in this case not wholly at one with the rest of the United Kingdom.”

At Holyrood, Nicola Sturgeon said it would be "unthinkable" if MSPs were not asked to give formal legislative consent to the repeal bill but added there was no "clear and emphatic acceptance" from the Conservatives at Westminster on the issue.

The First Minister called for clarity after Mrs May on Wednesday told MPs there was a ''possibility'' the bill, which overturns the 1972 Act which took Britain into the European Economic Community, would need an LCM in the Scottish Parliament.

"Despite the hints…there is still no clear and emphatic acceptance on behalf of the UK Government that the repeal bill will require the legislative consent of this Parliament.

"It is unthinkable that anything else would be the case, so maybe the Tories could just confirm that and stop prevaricating upon it?" added Ms Sturgeon.

But Mr Mundell appeared to give that confirmation, expressing confidence that Holyrood would agree to grant an LCM; to do otherwise would be untenable, he insisted.

"It would be incredible that the Scottish Parliament would, one, turn down a measure that would bring the body of European law into Scots law because if they don't there's incredible uncertainty and, two, decline additional powers and responsibilities.”

The secretary of state added: "We're very clear that the United Kingdom is the member state of the EU and while we will work very closely, as we have throughout, with the Scottish Government it will be the United Kingdom Government that will be conducting the negotiations."