SCOTTISH Tories have been left isolated in their support for Westminster in a looming constitutional battle over Boris Johnson’s bid to seize power from Holyrood – and law experts predict the row could end up in the UK Supreme Court.

The UK Government has sparked fury over plans to create powers over a UK “internal market” following Brexit which would force Scotland and Wales to accept any standards agreed in future trade deals.

Last week, Scotland’s Constitution Secretary Michael Russell wrote to Cabinet Office Minister Michael Gove urging him to scrap the proposals for the “biggest power grab yet” on Holyrood.

The Scottish Government has yet to receive a response to the letter, while details of the UK Government’s plans could be published this week.

Last week Scottish Tory leader Jackson Carlaw was criticised after describing the action being taken by the UK Government as “absolutely right”.

Other political parties at Holyrood have attacked the UK Government’s plans.

Alex Rowley, Scottish Labour’s Brexit and constitution spokesman, said the idea of the devolved administrations being ignored was “not acceptable”.

He said: “I think Carlaw has given up on fighting for what is best for Scotland and now the only thing that matters to them is what is best for Boris and his pals. It’s appalling.

“We have made it clear repeatedly we will work with the Scottish Government to protect the principles around environmental standards, food standards, health and safety standards.

“What we need to be doing is uniting the [Scottish] Parliament in urging the UK Government to work with the devolved administrations and the Scottish Government – we must have our say.”

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Scottish Greens co-leader Patrick Harvie said the UK “internal market” plans were “nothing more than a blatant attempt to undemocratically strip Scotland of powers it has used successfully for 21 years”.

Wendy Chamberlain MP, LibDem constitutional affairs spokeswoman, said devolved powers should be returned to Scotland.

She added: “We have also been clear that we want to see established EU standards on the environment and animal welfare endure. The Conservatives must not use Brexit as an excuse for a race to the bottom.”

Michael Russell has said the Scottish Government is prepared to take the issue to court over concerns it could jeopardise flagship policies such as minimum unit pricing for alcohol.

It is also feared a requirement to have the same regulatory standards across the UK could also lead to Scotland having to automatically accept lower standard imports such as chlorinated chicken, if they were permitted in England.

Professor Daniel Wincott, Blackwell professor of law and society at Cardiff University, said the indications were Wales and Northern Ireland may also have concerns about the legislation.

He said it could end up in a situation where all three devolved nations refuse to give legislative consent for the powers, but Westminster goes ahead anyway.

He said: “That raises really basic questions about the nature of the devolved institutions within the UK political system.

“These are questions that are of basic constitutional significance – they speak to questions about trust between the governments, they speak to the robustness of the devolution arrangements.

“We have been accustomed to talk about the devolution settlements, but this makes them feel very unsettled, much more vulnerable than the idea of a settlement would lead you to expect.”

Wincott said it was difficult to make any comment on what the legal basis of any challenge might be until the UK Government published a paper outlining the legislation. But he said if one can be found in Scots law, he would expect the Scottish Government to “move as quickly as possible”.

“There may be routes to the courts in each of the three legal jurisdictions – England and Wales, Northern Ireland and Scotland, although any litigation would likely end up in the UK Supreme Court,” he said.

“It is not at all clear how that would be resolved except to say that in all the Brexit litigation, the Supreme Court has emphasised a fairly conventional idea of the sovereignty of the Westminster Parliament. If Westminster passes legislation, that might well be the way the court ends up interpreting things.”

The UK previously followed the rules of the European Union internal market law, which allowed differences across the nations, as long as they met certain objectives. Now the UK Government wants to have the final say on areas overseen by devolved administrations, such as food safety, agriculture and the environment.

Russell has warned it is intent on taking action “under the cloak of Brexit” to weaken devolution.

In his letter to Gove, he said: “The information to hand leads the Scottish Government to believe that the purpose of such plans it not economic but is instead purely political.”

MICHAEL Dougan, professor of European law at the University of Liverpool, said while talks over the issue of a UK “internal market” had been ongoing for years, everyone had assumed there would be more time on it because a “rational government” would have extended the Brexit transition period.

“Now the Johnson Government has basically said we are not extending the transition, it means there has to be a solution in place in six months’ time,” he said.

“All the focus on Johnson’s refusal to extend transition has been essentially about relations between the EU and the UK – whereas in fact it is equally important for internal UK relations.

“By January 1, 2021 we need to know what the rules are which are actually going to govern trade within the UK – translating that it basically means what are going to be the constraints on the Scottish and Welsh parliaments?

“What is England going to do if Scotland wants to take a different path on the environment, or on agriculture? What if Scotland decided they do want to ban a certain type of plastic, for example, which England allows?

“What if Scotland decided they are going to ban chlorinated chicken, while Boris Johnson wants to have a trade deal with the US which might allow it in? These problems will happen and we need to know what the rules are.”

Dougan said the UK was almost unique among internal markets in the world as having one territory – England – make up 85% of the population and the economy.

That dominance is further magnified as there is “no distinction between UK institutions and English interests,” he added, while the political landscape means differing directions between the interests of the devolved nations and the UK Government.

“When you put those three challenges together, the consensus of all of us who have been talking about this for years now is there is no solution – at least no good solution,” he said.

“What we are looking at is the challenge of how to manage a bad situation in the least damaging way possible. That is the reality.”

Dougan said it was unlikely Johnson and his chief advisor Dominic Cummings would find an “excellent” solution to a problem which has “evaded civil servants in London, Edinburgh, Cardiff and Belfast for four years”.

“Although we don’t know what solution might emerge, I think we can be fairly certain it will be suboptimal, particularly from the perspective of Scotland and Wales,” he added.

Scottish Tory leader Jackson Carlaw last week claimed it was important to have some common key measures – such as food standards – across the UK to allow the internal market to operate.

“It’s absolutely no use whatsoever to Scottish farmers, to Scottish fishermen, to all the producers of food in Scotland if we end up with different standards to the rest of the UK,” He said. “It would seriously inhibit their ability to sell into that market.”