RUTH Davidson has been accused of carrying out a “stealth attack” on devolution after the Scottish Tories unveiled plans to lodge a “Union” amendment to the EU Continuity Bill which would severely constrain the Scottish Parliament’s powers.

The Scottish Government and Labour condemned the move which would ensure Holyrood could not pass laws affecting trade post Brexit which are out of step with Westminster’s.

Davidson’s constitution spokesman Adam Tomkins insisted the amendment was necessary “to protect the UK’s internal market”. But the Scottish Government said business is already conducted between Scottish and English firms where different regulations exist in certain areas.

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“This is yet another stealth attack by the Tories on devolution - if they can’t take Scotland’s powers away, they want to prevent us using them,” a spokeswoman for Scottish Brexit Minister Mike Russell said. “There are already differences in key policy areas which do not prevent trade within these islands or beyond it.”

The spokeswoman said if the Scottish Tories wanted to protect jobs and the economy, they would commit to membership of the European single market.

She added: “The biggest threat to Scotland’s ability to do business with the rest of the UK is of course Brexit, the risk of losing single market membership and the benefits that go with that.

“We are determined to do everything we can to protect Scotland’s interests in this process - we are continuing to negotiate with the Tory UK Government to try and agree on changes to their Withdrawal Bill that protect devolution.

“And we are also pressing ahead with our own EU Continuity Bill, which everyone but the Scottish Tories supports. This amendment simply confirms that Ruth Davidson’s Tories care more about the constitution than protecting jobs, businesses and livelihoods here in Scotland.”

Scottish Labour described the Tory move as “jaw-droppingly shameless”.

A party spokesman said: “The UK single market is the key market for Scottish businesses and any attempt to threaten it would do untold damage to our economy.

“But this attempt by Ruth Davidson to put a sticking plaster over her party’s attack on devolution is jaw-droppingly shameless.

“Their disregard of devolution at Westminster is causing further frustration and exasperation. The Tories should be protecting devolution and not playing games at Holyrood.”

The EU Continuity Bill is expected to be passed this week after getting the support of Labour, the Liberal Democrats and the Greens at earlier stages in the Holyrood process.It was brought in after the Scottish and UK governments reached a stalemate over the EU Withdrawal Bill at Westminster over the transfer of powers in devolved areas coming from Brussels.

The UK Government wants to hold onto 25 policy areas, including food standards, animal welfare and GM crops, until common frameworks are established. But the Scottish Government says Holyrood must agree with any new frameworks rather than them simply being imposed by Westminster. The measures in the Continuity Bill are designed to sidestep Westminster by giving Holyrood direct control over the repatriation of up to 111 EU powers into Scottish law.

Setting out “the union” amendment, Tomkins said: “The rest of the UK is Scotland’s biggest marketplace. Whatever else happens with Brexit, we must ensure we do nothing that damages access to it ... The best way forward is still for the SNP to back UK wide legislation. But if the SNP persists with its proposals, at least this amendment would deliver a ‘Union Guarantee’, making it clear that Scotland will not diverge from the rest of the United Kingdom in key areas such as regulation and case law.”