Published: 7:40 AM May 15, 2018 Updated: 8:44 AM September 18, 2020

A constitutional crisis is looming as the Scottish Parliament appears poised to formally refuse to give consent to Theresa May's Brexit legislation.

After months of wrangling with Westminster over where powers returning from Brussels should go after Brexit, the Scottish Government has submitted a motion making clear it does "not consent to the European Union (Withdrawal) Bill".

With the Greens, Scottish Labour and the Liberal Democrats having said they will join the SNP and vote against granting consent, it is certain to be passed when MSPs vote on the matter at 5pm.

Such a move would not prevent the UK government from introducing the legislation - but it would be the first time Westminster has pushed through laws against the wishes of the Scottish Parliament.

Scottish Government Brexit minister Mike Russell said Mrs May's administration in Westminster had "no mandate" to "undermine the devolution settlement".

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He said the plan, which could see some powers kept by the Westminster Parliament for up to seven years, "rides roughshod over devolution".

"Devolution is the settled constitutional will not just of the Scottish people, of the whole of the UK," he told BBC Radio 4's Today.

"Westminster is trying to subvert that and to change that by the back door."

Mr Russell added: "The Parliament will vote to reject legislative consent for the Withdrawal Bill - not just the Scottish National Party in government, I think all the parties save the Conservatives will actually vote for that."

The Scottish Tories called on Labour and the Liberal Democrats to join with them in supporting the legislation rather than siding with the SNP.

Tory MSP Adam Tomkins said: "The Scottish Conservatives will vote to give our consent to the amended Withdrawal Bill today.

"It's profoundly regrettable that we don't have a deal in Scotland to allow us to move on.

"The blame for that lies entirely with the SNP. Nicola Sturgeon has refused to compromise. It's not in Scotland's interests that the SNP prefers picking fights to making a deal."

He added: "It's obvious that the Greens will, as always, back the SNP today.

"But we would appeal to Scottish Labour and Scottish Liberal Democrat MSPs to think hard before siding with the nationalists."

But Scottish Labour's Brexit spokesman Neil Findlay said: "As the party that delivered devolution, Labour will always seek to defend and strengthen it.

"The problems with clause 15, formally clause 11, mean that Labour will vote against the principle of legislative consent for the EU Withdrawal Bill at Holyrood today."

He added the Tories' "shambolic handling" of matters meant the issue could be resolved in the Supreme Court - where judges will rule if the Scottish Government's alternative Continuity Bill falls within Holyrood's legislative competence.

Scottish Green co-convener Patrick Harvie was also clear his party's MSPs would "not consent to the UK government's assault on the powers of the Scottish Parliament".

Meanwhile, Scottish Liberal Democrat Europe spokesman Tavish Scott said: "The Brexit process has been chaotic and the treatment of the devolved administrations has been shoddy."

Scottish secretary David Mundell defended the UK government's position, telling Today: "Obviously, it's up to the Scottish Parliament to take whatever decision they want to take.

"I still hope that they will take a positive decision, that they will take a step back and look at the proposal that we have put forward in relation to the specific arrangement which is just to keep 24 areas which affect the whole of the UK exactly as they are at the moment, so that the day after we leave the EU nothing will have changed.

"Then there will be an opportunity to have a discussion across the whole of the UK as to what new arrangements should replace those which are already in place. I just don't see how that can be characterised as a power grab."