UK Government lawyers have swept aside Holyrood’s Brexit fears and urged the UK Supreme Court judges to “resist the invitation” from the Scottish Government to make a political judgement and stick to the law.

On Monday, a four-day hearing begins - regarded as the most significant court battle on constitutional matters in modern times – in which the UK Government will appeal against the High Court’s ruling that Theresa May cannot use so-called prerogative powers to trigger Article 50 and that MPs should have a vote on the Prime Minister’s Brexit strategy. The Scottish Government has been given leave to intervene to put its case: that MSPs should have a vote too.

Whitehall lawyers have now responded to the initial submission by James Woolfe QC, the Lord Advocate, on behalf of the SNP administration and dismissed out of hand its case.

But the tone of the response from Jeremy Wright, the Attorney General, who is leading for the UK Government, has drawn stiff criticism.

Sir Paul Jenkins QC, a former head of the UK Government’s legal department and Permanent Secretary to the Attorney General from 2006 to 2014, tweeted: “I can't recall a case where the Govt thought it wise to descend to such rudeness. Unnecessary and inappropriate,” while Jolyon Maugham QC described Whitehall’s response as “fantastically rude”.

He tweeted: “Translated from lawyer, para 39 says the Welsh assembly is wrong but, unlike the Scottish Government, at least is not stupid to boot.”

Paragraph 39 of the UK Government’s response refers to the arguments made by Cardiff and Edinburgh regarding the Sewel Convention - which states the UK Government will not normally legislate on devolved matters without Holyrood's consent - and notes how the point made by Mick Antoniw, the Counsel General for Wales, “in contrast to that of the Lord Advocate, at least has the merit of focusing on the issue of use of the prerogative, which is the issue before the Court”.

Mr Woolfe, who cited the Act of Union and Claim of Right in his initial submission, argued that Brexit would have a major impact on the Scottish Parliament’s devolved powers and, under the Scotland Act which created devolution, such changes "may not be affected by an act of the executive alone".

The Lord Advocate said a legislative consent motion from Holyrood under the Sewel Convention would be needed; that is, a vote.

But in response to Edinburgh’s submission, Mr Wright, together with Lord Keen, the Advocate General for Scotland, Whitehall’s top Scottish lawyer, note how the High Court or Divisional Court[DC] in its hearing earlier this month did not deal with the issue of devolved legislation.

“With the greatest of respect to the Lord Advocate and the Counsel General, the DC was right to conclude that points arising from or in relation to the devolution legislation, or from Scots law, add nothing material to the issues in this appeal,” argues Mr Wright.

In countering the Scottish Government’s case, the Attorney General goes on to say: foreign affairs, including EU matters, are reserved to Westminster; Scots law recognises the UK Government’s prerogative powers just as English law does and nothing in the Article 50 notification or “indeed withdrawal from the EU altogether”, alters the “existence of”, the “essential structure” of and "architecture" of the devolution settlements.

On the Sewel Convention, Mr Wright highlights how it is just that: a political convention. He points out how it says Westminster would “not normally legislate”.

“Whether circumstances are ‘normal’ is a quintessential matter of political judgement for the Westminster Parliament and not the courts. There are no judicial standards by which to measure such a question in the context of a political convention,” he argues.

The Attorney General adds: “The Court is being invited by the Lord Advocate and the Counsel General to stray into areas of political judgment rather than legal adjudication. The Court should resist that invitation, particularly where the underlying issue is one of considerable political sensitivity.”

The political ramifications from the court case could be highly significant because if the judges rule in favour of MSPs having a vote, then Holyrood could veto Mrs May’s Brexit strategy.

Given the importance of Brexit on the UK economy, the PM might feel, in those circumstances, the only way she would be able to put into effect her preferred approach would be to seek a public mandate - through a general election.