Tories pushing for a hard Brexit are putting devolution in Scotland at risk, the country’s Deputy First Minister has warned.

John Swinney claimed that key legislation necessary for Britain to leave the European Union “undermines the principles of devolution and the powers of the Scottish Parliament that the people of Scotland campaigned so long to win”.

The Scottish Government’s repeated insistence that the European Union (Withdrawal) Bill is a “power grab” comes as Theresa May was accused of being “too weak” to face down hardline Brexiteers in her party after more than 60 Conservative MPs set out their demands for the next stage of exit talks.

UK Brexit Secretary David Davis will meet senior figures from the devolved administrations in London on Thursday in a bid to resolve the deadlock between Holyrood and Westminster.

With discussions taking place Mr Swinney said the “next few weeks are likely to be as important for Scotland’s future as any in our recent history”.

The Scottish Government has already produced a report claiming a hard Brexit, with Britain leaving the EU without a trade deal, could cost Scotland’s economy £12.7 billion a year by 2030.

Writing in the Daily Record newspaper, Mr Swinney said: “Despite the overwhelming vote in Scotland for Remain, the Tories are pursuing a hard Brexit no matter the cost to jobs and living standards.

“Brexit poses a threat not just to our economy – it is now a threat to the hard-won devolution settlement which people in Scotland voted for so decisively in 1997.”

Scottish Brexit Minister Mike Russell, who will represent the Scottish Government in the talks on Thursday, said on Twitter that a deal could still be done, but only if the UK Government wanted to.

He said: “A deal can only be done in London tomorrow if @GOVUK wants to agree on frameworks rather then impose them. Westminster proposals aim to take away Scotland’s say on most important issues.”

The Scottish and Welsh administrations have repeatedly warned that clause 11 of the EU Withdrawal Bill is a “power grab”, as it transfers devolved powers currently held by the EU to Westminster in the first instance – something the Conservative Government insists is necessary to allow common frameworks to be set up across the UK.

With UK ministers having so far failed to bring forward amendments to the legislation, Mr Swinney said it “remains a powers grab in critical areas at the heart of the devolution settlement”.

SNP ministers at Holyrood are “simply seeking to protect the devolution settlement and to ensure the Scottish Parliament has the powers in full that the people of Scotland voted for”, he added.

“We will never recommend giving consent to a Bill that undermines the principles of devolution and the powers of the Scottish Parliament that the people of Scotland campaigned for so long to win.”