Both parties are expected to vote alongside Nationalist and Green MSPs in formally refusing to give consent to Theresa May’s EU Withdrawal Bill.
The First Minister’s administration has refused to sign up to a compromise agreed with the Welsh Government, maintaining it represents a “power grab”.
Scottish ministers argue it still gives Westminster the “final say” over a series of frameworks to prevent the UK’s internal market being fractured.
Click here to READ MORE
Conservatives insist significant changes have been made to address concerns over devolution and accused the SNP of trying to whip up support for independence.
Scottish Tory constitution spokesman Adam Tomkins urged Labour and the Lib Dems to back the Bill, blaming Nationalists for the failure to reach agreement.
He said: “Nicola Sturgeon has refused to compromise. It’s not in Scotland’s interests that the SNP prefers picking fights to making a deal.
“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.
“Let’s be clear: Labour and Liberal Democrat support would not amount to backing for the UK Conservative Government. They would be supporting our United Kingdom and our established system of devolution.”
But Scottish Labour’s Brexit spokesman Neil Findlay said remaining problems meant his party will “vote against the principle of legislative consent”.