MPS have been warned that ignoring the Scottish Parliament’s vote would be “an unprecedented step for which there is no justification” when they come to debate the UK Government’s EU Withdrawal Bill today.

Scottish Brexit Minister Michael Russell said failing to respect the vote by MSPs to withhold consent “must not happen” and that the legislation must be changed.

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Labour, the LibDems, the Greens and the SNP all opposed the bill when it was voted on in the Scottish Parliament last month. Speaking ahead of the Westminster debate, Russell said he hoped MPs wouldn’t be willing to risk the constitutional crisis that would arise from passing legislation that didn’t have consent from Holyrood.

“The overwhelming vote in the Scottish Parliament made it perfectly clear that consent will not be given to the EU Withdrawal Bill as long as it contains measures that could constrain the powers of the Parliament without its agreement,” Russell said. “Under the rules of our constitutional arrangements, the Westminster Parliament has never passed legislation on devolved matters against the wishes of the Scottish Parliament. Ignoring the Scottish Parliament’s vote would be an unprecedented step for which there is no justification – that must not happen.”

Both the SNP and Labour have tabled amendments to Clause 15, the so-called power-grab clause. Russell said the SNP’s changes would simply remove the clause that “allows for devolved powers in key areas to be frozen for up to seven years without agreement” and without impacting on the Government’s ability to “deliver common arrangements, where these are in Scotland’s interests”.

Labour’s change would seek to cut from five years to three the proposed post-transition period “sunset clause”, regulating how long Whitehall could keep control of the powers coming back from Brussels. They also propose that consent from the Scottish Parliament must be sought unless the UK Government has to legislate in an area which involves an international obligation.

Labour shadow secretary of state for Scotland Lesley Laird said her party had “tried to find solutions throughout this process that deliver a result for the people of Scotland”.

“Labour has been the only party making a serious attempt to break the Brexit deadlock, and these proposals are a serious attempt to stop the UK heading towards a constitutional crisis over devolution,” she claimed.

But the SNP said Labour’s plans didn’t go far enough. The SNP leader at Westminster, Ian Blackford, warned that Labour could leave “the door open to the Tories’ power grab”. “Their proposals continue to allow Holyrood’s powers to be constrained and controlled without Holyrood’s consent – going way beyond the current Scotland Act. That is something which Holyrood refused consent for last month by an overwhelming majority including all parties except the Tories,” Blackford said.

However, the pleas of Blackford, Laird and Russell will likely be fairly low down on Theresa May’s list of things to worry about during today’s debate, as those are votes she probably won’t lose.

Last night, she made a rare appearance in front of her MPs, where she appealed for unity on revoking the 15 amendments made to the bill in the Lords, warning that defeat in the Commons could lead to the collapse of her government.

The Prime Minister, who currently has a notional majority of just 14, faces a sizeable rebellion on a number of votes, including plans to give parliament a meaningful final say on the Brexit deal, and on a push to keep the UK in the EEA customs union after departure.

She added: “The message we send to the country through our votes this week is important. We must be clear that we are united as a party in our determination to deliver on the decision made by the British people.”

May faces a rebellion on both sides, with neither the Remainers nor the Leavers on her backbenches happy.

Downing Street believes it has the numbers to get the Lords amendments undone, but the Tory rebels warned Number 10 not to be so sure.