The Scottish Parliament is set to formally refuse consent to key UK Brexit legislation in an unprecedented move.
MSPs from the SNP, Labour, the Greens and the Liberal Democrats are expected to unite to back a Scottish Government motion withholding parliamentary consent for the EU Withdrawal Bill.
Only the Scottish Conservatives have said they will vote against it and back UK ministers.
This means the motion is likely to be decisively endorsed when Holyrood votes on it at around 5pm on Tuesday.
This would not prevent the UK Government from introducing the legislation, but if it did so it would be the first law passed at Westminster against the formal wishes of the Scottish Parliament.
The controversial Withdrawal Bill has caused a months-long row between the Scottish and UK governments over devolved powers post-Brexit.
The UK’s proposed legislation has long been dubbed a “power grab” by the Scottish Government.
It is angered by measures in the bill which would see some powers held by the EU not immediately passed to them despite coming under devolved policy areas.
UK ministers reached a deal with the Welsh Government, which had initially joined Nicola Sturgeon’s administration in its opposition to the UK bill.
But Scottish Brexit minister Michael Russell said even that deal could see some powers kept by Westminster for up to seven years.
He insisted Theresa May’s government has “no mandate” to “undermine the devolution settlement” and that the Withdrawal Bill “rides rides roughshod over devolution”.
‘This is not some abstract issue – this covers key policy areas such as farming, food and drink, fisheries and protecting the environment.’
Scottish Brexit minister Michael Russell
“Devolution is the settled constitutional will not just of the Scottish people, of the whole of the UK,” he told the BBC.
“Westminster is trying to subvert that and to change that by the back door.”
He added: “This is not some abstract issue – this covers key policy areas such as farming, food and drink, fisheries and protecting the environment.”
However, the Scottish Conservatives back the changes made to the bill as part of the UK Government’s wrangling with the Scottish and Welsh governments.
The party has called on Scottish Labour and the Scottish Liberal Democrats to “think hard” before backing 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.
Judges in the UK’s highest court will rule if the Scottish Government’s alternative Continuity Bill falls within Holyrood’s competence after Theresa May’s government mounted a legal challenge against it.
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”.
Europe spokesman for the Lib Dems, Tavish Scott, said: “This bill has come a long way from the sorry piece of legislation that was first laid before Parliament but we still cannot support it.
“The Brexit process has been chaotic and the treatment of the devolved administrations has been shoddy.”