In a letter to all MSPs, Michael Russell said the amendments put forward to the EU (Withdrawal) Bill would leave Westminster able to “unilaterally impose changes to devolution” and fall “well short” of those the devolved administrations wanted.

Mr Russell’s letter was dispatched as UK ministers tabled the amendments in the House of Lords.

The bill will transpose EU law into UK law following Brexit but the Scottish and Welsh governments claim it is a “power grab” amid a row about the repatriation of devolved powers from Brussels.

John Swinney and Brexit minister Michael Russell arriving for talks last November

Mr Russell wrote: “The amendments replace the previous blanket reservation of devolved areas which are subject to retained EU law, with a power for the UK government to make regulations in the UK Parliament imposing such a restriction in any such devolved areas. In exercising this power, the UK government would only be under a duty to consult the devolved administrations and provide information to the UK Parliament on the effect of the regulations and that consultation. There would be no need for such changes to be agreed by the devolved Parliaments or governments.”

He said this means Downing Street could “make regulations notwithstanding the opposition of the devolved administrations, entirely at its discretion, with no safeguards to protect the interests of the devolved legislatures”.

He said matters covered by the regulations would be reserved, if only temporarily, leading to uncertainty over whether the Sewel convention would apply, which the UK government has not clarified.

Mr Russell also said there was no sunset clause on the proposed regulations. Downing Street insisted the UK government wanted to reach an agreement and Theresa May is set for talks with Scottish and Welsh first ministers Nicola Sturgeon and Carwyn Jones tomorrow. “This is a very important piece of legislation for delivering a smooth Brexit and we continue to engage with the devolved administrations to reach agreement on this,” the Prime Minister’s spokesman said. “What we are focused on is reaching agreement.”

Cabinet Office minister David Lidington said: “Our amendments respect and strengthen the devolution settlements across the UK but still allow the UK government to protect the vitally important UK common market, providing much-needed certainty and no new barriers to doing business.”

SNP Minister: Amendments to Brexit bill '˜fall well short'