Responding to James Wolffe QC, the Attorney General, Jeremy Wright QC and the Advocate General for Scotland, Lord Keen of Elie QC said: “With the greatest of respect to the Lord Advocate and the Counsel General, the DC was right to conclude that points arising from Scots law add nothing material to the issues in this appeal.”

Sir Paul Jenkins QC, former head of the UK government’s legal department and Permanent Secretary to the Attorney General between 2006 and 2014 tweeted: “I can’t recall a case where the Govt thought it wise to descend to such rudeness. Unnecessary and inappropriate.”

Jolyon Maugham QC called the response “fantastically rude”, and tweeted: “Translated from lawyer, para 39 says the Welsh Assembly is wrong but, unlike the Scottish Government, at least is not stupid to boot.”

In a comprehensive submission to the Supreme Court detailing the Scottish government’s argument that the triggering of Article 50 requires an act of Parliament, the Lord Advocate noted that Art.50(1) TEU states that withdrawal is to be made in accordance with a member state’s “own constitutional requirements”.

He added that because withdrawal would change the Scottish Parliament’s competence and that of the Scottish government as well as the law within devolved competence, the Sewel Convention is engaged — in terms of which Parliament “does not normally legislate with regard to devolved matters without the consent of the Scottish Parliament.”

Mr Wolffe made a number of other arguments including the fact that it is a matter of constitutional principle that laws cannot be changed or repealed by means of the Royal Prerogative alone.

His submission noted that “This principle is reflected in the Claim of Right Act 1689 and in Article XVIII of the Acts of Union of 1706 and 1707.”