The First Minister has warned Holyrood could withhold consent over the UK Government’s Great Repeal Bill in a battle over the repatriation of powers.
Prime Minister Theresa May has pledged the Scottish Parliament will see a “significant increase” in decision-making after ties are cut with Brussels.
But Ms Sturgeon repeated claims Westminster is staging a “power grab” because it has refused to guarantee Edinburgh will gain full control over areas such as farming and fisheries.
Her warning comes ahead of a formal request to stage another independence referendum and could derail the sweeping plans to transfer EU laws on to the UK statute books.
Under the 1998 Scotland Act, fishing and agriculture are not explicitly reserved and so are devolved by default.
But the new Bill – ending the European Union’s legal supremacy – will create a “common UK framework” of trade regulations to ensure the “effective functioning of the UK single market is maintained”.
Scottish Secretary David Mundell has previously said he was “working on the basis” that a legislative consent motion (LCM), the formal device used for Holyrood to give permission for Westminster to legislate in devolved areas, would be needed.
He also warned a failure to secure MSPs’ backing for the Bill would have “very significant consequences” by leaving “a whole” in Scots law.
Unveiling a White Paper, Brexit Secretary David Davis said ministers “don’t know” yet if permission would be needed from Holyrood and other devolved legislatures in Wales and Northern Ireland.
But pledging talks on the issue he told MPs: “No powers currently exercised by them will be taken away. We’ve said that time and again.
“We also expect there to be a significant increase in the powers exercised by the devolved administrations.
“But I say this – we have to maintain the United Kingdom internal market too.
“That is four times as important to Scottish businesses, for example, as the European market.”
However Ms Sturgeon used her weekly question session at Holyrood to launch a renewed attack insisting powers should “automatically come to this chamber”.
The First Minister added this “leads me to suspect that what the Tories are actually planning is a power grab on this parliament, and that will be absolutely unacceptable.”
Her Brexit Minister Mike Russell also claimed the White Paper “leaves many important questions unanswered, such as the nature of the powers for the Scottish Parliament, and the need for the consent of the Scottish Parliament.”
He said: “In all other areas where powers already belong to the Scottish Parliament, the white paper continues to threaten that in areas such as agriculture, fisheries and the environment, powers will be taken by the UK Government after Brexit.
“For the UK Government to seek to impose legislative frameworks on these areas would be to take the unprecedented step of extending its powers over Scotland and must not take place. The Scottish Parliament’s competences must not be diminished as a result of Brexit.”
Later asked if the Scottish Government would not grant consent to the Bill, the First Minister’s spokesman replied: “In terms of the removing competence element, we wouldn’t in those circumstances be giving legislative consent.
“We have no intention of facilitating or enabling the removal of powers from this parliament.”
The Great Repeal Bill has been hailed as an essential part of leaving the EU, with thousands of rules covering everything from workers’ rights to the environment scrapped or replaced with UK equivalents.
It also means the UK Supreme Court will be the highest court in the land from day one of Brexit, replacing the EU court in Brussels.
Observers widely expect it to require at least in part an LCM because it will change devolved ministers’ competencies.
It will hand them same so-called “Henry VIII powers” as their UK counterparts to transform directives into “secondary legislation” that require less parliamentary scrutiny to be altered or dumped.
While withholding consent could stall the Bill’s progress, some experts believe the UK Government could simply ignore Holyrood’s wishes.
But this would provide more political ammunition for the SNP and risk a court battle.
Meanwhile, Ms Sturgeon is expected write to Mrs May today to formally request the Section 30 order needed for another independence vote.
It follows Tuesday’s controversial Holyrood vote backing her plan despite UK ministers signalling they will not allow a ballot for at least five years.
Scottish Tory constitution spokesman Adam Tomkins said: “The SNP is complaining about the return of substantial new powers which – under its plans – would remain in Brussels. If ever people needed to see their utter hypocrisy, this is it.
“As the Prime Minister has made crystal clear, the UK Government expects substantial new powers to be delivered to our devolved parliaments as a result of Brexit.
“Mike Russell and his colleagues now need to ditch the petty politicking and work with the UK Government to make this plan work for all of us, here in Scotland, and elsewhere in the UK.”
Scottish Labour’s Westminster spokesman Ian Murray added: “The White Paper says that the government expects ‘a significant increase in the decision making power of each devolved administration.’
“That is what Scottish Labour wants for Scotland and the UK and Scottish Governments must work together to achieve this.”
A UK Government spokeswoman 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.”