CONSTITUTIONAL warfare over Brexit intensified yesterday as the Scottish Government raised the prospect of frustrating a major part of the process amid fears Westminster could carry out a “power grab” on Holyrood.

Nicola Sturgeon has previously spoken about the issue after Theresa May indicated earlier this month that powers being repatriated from Brussels in devolved areas, such as agriculture, fishing and the environment, could remain in London rather than pass to Edinburgh.

Yesterday, the First Minister’s spokesman went further, suggesting Holyrood would try to block the landmark UK legislation, the Great Repeal Bill, which will transfer thousands of European regulations into British law, should it encroach on Holyrood’s authority.

He said legislative consent to any bill which removed competences from Holyrood, such as powers over agriculture and fishing, would not be given.

Moreover, on the issue of Scotland holding a second independence referendum, Sturgeon yesterday drafted a letter formally asking for the powers to do so.

The Scottish Government released a photo of her penning the letter to the Prime Minister, which she is expected to send today, from her sofa in Bute House.

On the issue of repatriating powers, the First Minister’s spokesman said: “If the intention that aspects of farming and fishing affecting Scotland are no longer to be fully exercised by this parliament but by Westminster then they would have to reopen the Scotland Act 1998. [To do so] they will have to break open the founding statute of this Parliament and go against the founding principles of devolution.”

Asked if the Scottish Government would block the entire Great Repeal Bill, the spokesman added: “We have no intention of facilitating or enabling a removal of powers from this Parliament.”

The development came amid increasingly tensions between the First Minister and the Prime Minister who met in Glasgow on Monday.

Relations have been strained over a range of issues including the refusal by the Prime Minister of the Scottish Government’s request for a bespoke Brexit deal that would allow Scotland to remain in the European single market as part of the UK. May has also refused to hand Holyrood the powers to hold a new referendum before the UK leaves the EU in Spring 2019.

The Prime Minister has said she wants to give more powers to Holyrood following Brexit, but with no specific ones mentioned there is suspicion this will not happen.

The row over the Great Repeal Bill took up part of yesterday’s First Minister’s Questions when Sturgeon agreed with Scottish Greens co-convener Patrick Harvie that the devolved administrations had so far been treated “with contempt” in the Brexit process.

Harvie told MSPs: “Today, the UK Government is publishing its absurd Repeal Bill covering huge areas of power which have no place being exercised by UK ministers.

“Can I ask what the First Minister’s view is on the scope of that Repeal Bill? Does she agree that it must not be allowed to change legislation that is not specifically reserved under the Scotland Act?”

Sturgeon said: “The issue, of course, around the Great Repeal Bill is about powers currently with the EU, that if they are to be repatriated in areas that are currently wholly devolved – agriculture, fishing, for example – where should those powers go?

“Now, under the current terms of the Scotland Act, those powers should automatically come to this chamber but nobody in the UK Government, and I discussed this with the Prime Minister on Monday, nobody on the Conservative benches will give that guarantee, which leads me to suspect that what the Tories are actually planning is a power grab on this parliament, and that will be absolutely unacceptable.”

She added: “I think it’s really important that everybody across this chamber stands up for the rights of this Parliament before we go any further in this process.”

Sturgeon said the Scottish Government had not seen Wednesday’s letter triggering Article 50 before it was published and did not know in advance when it was going to be published or what it would say.

“Not just Scotland but all of the devolved administrations have been treated with contempt by the UK Government so far in this process,” she said.

In a swipe at May, she added: “To be fair, though, the Prime Minister did give me an insight into its contents on Monday of this week.

“She told me, and this is a direct quote, she told me that the Article 50 letter would be not detailed, not short but not lengthy either. So I’m grateful to her for that insight into the Government’s thinking.”

The Bill will see thousands of EU laws on everything from workers’ rights to the environment scrapped or replaced with UK equivalents.

Stephen Gethins, the SNP’s spokesman on Europe, echoed the First Minister’s concerns after Brexit Secretary David Davis gave details of the Bill in the Commons.

Gethins said Davis was unable to say what legislative consent motions would be required from the Scottish Parliament for the Bill to be passed.

“It is unbelievable that David Davis is still unable to say where the Scottish Parliament’s legislative consent will be required, what powers will go from Brussels to the devolved administrations, or whether the UK Government will attempt to use Brexit to roll back devolution,” he said.

The issue of legislative consent motions – the mechanism used by Holyrood to pass Westminster legislation relating to devolved areas – came to the fore in the Supreme Court judgement over the Article 50 Bill, when the court ruled they could be over-ruled by Westminster.

Should Westminster seek to counter any action by Holyrood over the Great Repeal Bill the move would again highlight the Scottish Government case about weaknesses in the devolution settlement.

The row potentially gives the Scottish Government some leverage in their ongoing stand-off with May over Brexit and consent for a referendum.

The First Minister is today expected to send her letter to the Prime Minister requesting the Section 30 order, the legal power to hold a new plebiscite.

Last night Scottish Labour MP Ian Murray said all repatriated powers in devolved areas should return to the devolved administrations.

A UK Government spokesman said: “We have published a White Paper on the Great Repeal Bill. The legislation itself will be brought forward at a later date. The final content of the bill will determine the process to take it forward.”