After months of discussion behind closed doors, the public will finally get to see the detail of which devolved powers being repatriated from Brussels that Westminster wants to keep temporary control of, with the publication of a list within the next few days.

But the Scottish Brexit minister Michael Russell complained he had not been shown the document, or agreed to it, and suggested the leaking of an internal UK Government letter yesterday confirming publication of the list was an underhand negotiating tactic.

The dispute will be taken up by Nicola Sturgeon and Theresa May at a meeting next week, but Scottish Secretary David Mundell warned it could drag on until after Easter.

David Liddington, left, and Michael Russell

A Cabinet Office letter, obtained by the BBC, revealed that UK ministers are concerned it is becoming “difficult to counter” claims of a power grab over around 25 out of 111 powers in devolved areas such as agriculture and fisheries.

An amendment to the EU Withdrawal Bill, which will put post-Brexit devolution plans into law, is also set to be published early next week despite a lack of agreement on its wording.

“We made our concern clear about an attempt to bounce us into a list of issues, which we had not seen,” Mr Russell said after Thursday’s meeting.

“It shows the extraordinary nature of the power-grab that’s underway. Mr Mundell said the list of powers would be published because “it’s more difficult to have that discussion in a vacuum”.

He denied that the process had “drifted”, with the Scottish Secretary admitting the dispute could go “to the wire” with wrangling carrying on until May, when the Withdrawal Bill is due to be passed by the House of Lords.

In a sign that the Welsh Government, which has joined the Scottish Government in demanding full devolution of all returning powers, could be closer to accepting the UK Government’s offer, Welsh minister Mark Drakeford said Cardiff was content for certain powers to be put in a Westminster “freezer”, provided that Whitehall provided certain assurances.

“We need to agree which powers are going into the freezer, how long are they going to stay in the freezer, and how are we going to get them out of the freezer,” Mr Drakeford said.

He added that a “political agreement” could be reached between government leaders next week. “If I was to be optimistic, what I hope we could get to next week would be a political agreement that we have found a path through the remaining obstacles to an agreement and that what we now have to do is... turn that political agreement into the words on a page,” Mr Drakeford said.

Cabinet Office minister David Lidington said: “The UK Government has a proven track record on devolution, our amendment is reasonable and we have moved a considerable way on it.”

UK ministers accused of trying to '˜bounce' Holyrood into Brexit deal