Labour have called on Scottish Conservative MPs to back their amendment to key Brexit legislation to protect devolution.
The EU Withdrawal Bill is due to begin its final stage in the House of Commons on Tuesday without changes to a clause governing devolution.
The controversial clause 11 means all devolved powers returning to the UK from Brussels will initially go to Westminster, which the Scottish and Welsh administrations have branded a "power grab".
The UK Government claims the move is needed to set up UK-wide frameworks in some areas and it will help devolved further power to Holyrood.
Labour's Shadow Scottish Secretary Lesley Laird and Shadow Brexit Secretary Keir Starmer have written to Scotland's Tory MPs urging them to vote for Labour's amendment.
Ms Laird said: "The EU Withdrawal Bill as it stands drives a coach and horses through the devolution settlement. That is simply unacceptable.
"The Secretary of State has broken his promise that this legislation would be fixed to protect the principles of devolution.
"The Bill can still be changed before it goes to the House of Lords - Labour's amendment today can fix these problems.
"That's why Labour has written to Scottish Tory MPs urging them to back our amendment - and protect the devolution settlement."
The Scottish and Welsh administrations are refusing to grant legislative consent for the Bill until the clause is amended.
Scottish Conservative constitution spokesman Adam Tomkins has said the Bill needs to be amended to comply with the devolution settlement.
Meanwhile, the SNP challenged Labour leader Jeremy Corbyn to "get off the fence" on Brexit and back staying in the single market and customs union.
Last week, Mr Corbyn was empty-chaired at a SNP-organised cross-party Westminster summit aimed at preventing a hard Brexit at which SNP, Liberal Democrat, Plaid Cymru, and Green Party leaders committed a joint amendment to the EU Withdrawal Bill.
Stephen Gethins MP said: "Time is running out to prevent the economic catastrophe of an extreme Tory Brexit.
"Jeremy Corbyn must now get off the fence, show some leadership and get behind efforts to protect our vital membership of the single market and customs union - before it is too late.
"If Labour continue to support reckless Tory plans for a hard Brexit, they will be guilty of destroying jobs and slashing the incomes, livelihoods and living standards of millions of people."