BREXIT isn’t damaging devolution but strengthening it, David Mundell will insist today, less than 48 hours after Sir John Major warned it could lead to Scottish independence.

The Scottish Secretary will also use a speech in Edinburgh about 20 years of devolution to reject SNP claims Westminster has conducted a ‘power grab’ under cover of Brexit.

He will say: “I reject completely the argument put forward by opponents of devolution that it has been crushed by Brexit.

“I do not believe Brexit will damage devolution. I want it to strengthen devolution, and I believe that can and will happen.

“Leaving the EU will bring new powers to Holyrood and new responsibilities to the Scottish Government.”

The comments are dramatically at odds with those of Sir John, who warned the “agonies of Brexit” could end devolution and the Union.

In a speech at Glasgow University attacking the “zealots” of the European Research Group of Tory Brexiter MPs, the former Tory PM said: “I find it painful to come to terms with the possibility that, within my lifetime, I could - I repeat could - see the break up of the UK.”

“I hope I am wrong, but the agonies of Brexit have the capacity to do just that.”

Mr Mundell also say SNP warnings of a Brexit-related ‘power grab”, with Westminster hoarding powers that ought to be returned from Brussels to Holyrood, have proven to be a “complete fantasy” and an “invented grievance”.

He will say: “To listen to the rhetoric coming from some of my political opponents, you could be forgiven for thinking that Holyrood is being stripped of a whole raft of powers it currently exercises.

“The reality is that more than 100 powers previously exercised in Brussels will transfer to Edinburgh on the day we leave the EU.

“To characterise this process as a ‘power grab’ is nonsense.

“We should remain deeply suspicious when opponents of devolution try to present themselves as its champions and protectors.”

SNP deputy leader Keith Brown said: “The Tories fought tooth and nail against devolution in the first place – and their attitude has barely changed since.

“David Mundell is perfectly content with imposing a hard Brexit on Scotland against our will - while making a power grab on areas the Leave campaign pledged would come directly to Holyrood.”

In a separate speech today, UK communities Secretary James Brokenshire will say the Tories are offering “a new Unionism”.

Acknowledging the Yes campaign and Brexit posed questions for the union, he will say these “must be answered with confidence”.

He will say: “We must make the case for a new unionism, and explain more readily the value and meaning of being a citizen of our United Kingdom. The rights we have, the values we share, the benefits we enjoy and the duties we owe.

“These should be things that not only we cherish, but that people from around the world aspire to have too. Only the Conservatives are able to offer this sort of national renewal.”