BORIS Johnson must not " ride roughshod" over devolution, a veteran Conservative politician has warned.

Lord Patrick Cormack also told his fellow peers there was a rising 'English nationalism' in his party that had to be 'headed off'.

An MP for more than 30 years, Lord Cormack warned that the UK Internal Market Bill had further consequences for the country than just breaking international law during a debate on the legislation today.

The Bill is undergoing detailed line-by-line scrutiny in the House of Lords, and is scheduled for four days of consideration.

The controversial legislation sets out the way that trade within the UK will work once it is outside the EU’s single market and customs union, however parts of it break international law.

Cross-party amendments have been tabled to strike out clauses linked to the most contentious part of the Bill, which aim to give ministers the power to breach the Brexit divorce deal – known as the Withdrawal Agreement – brokered with Brussels last year.

This afternoon Lord Cormack said: "We cannot ride roughshod over what has now been established for some 20 years or more. If we do we will truly endanger the future of the UK.

"It would be a constitutional and political tragedy if, a decade from now we had Northern Ireland broken away, maybe Wales, but almost certainly Scotland.

"As a member of a mongrel family, a large proportion of which still lives north of the border, I would feel that would be the ultimate betrayal of the British Parliament, of the union it is our duty to safeguard.

"I hope that as we go through this bill we will remember how crucially important it is that the United Kingdom should survive."

He said he hoped the Government "will take on board the seriousness of this threat, this danger to our country" adding it should "head off the the forces of English nationalism which seem to be a little too predominant in my party on the moment."

The peer explained that he was "not an advocate of devolution" in the 70s, but added: " The fact is, we do have devolution and we cannot ignore what we have or we will truly endanger the future of the union. And that we must not do."

Green Party peer Baroness Jones of Moulsecoomb said the Government was using Brexit as an excuse to “take more control of the country” and accused ministers of creating a “Frankenstein’s monster” to “grab more power”.

But business minister Lord Callanan rejected their criticisms, saying: “We are not riding roughshod over the devolution settlements.

“Devolved administrations will acquire dozens of new powers they have not exercised before once we leave the EU transition period.

“This Bill is about ensuring that those powers are exercised in a non-discriminatory manner."