Ministers announced last week they would press ahead with a Scotland-only Brexit Bill at Holyrood, despite Presiding Officer Ken Macintosh judging it to be outwith the Scottish Parliament’s Powers. This is the first time any Scottish Government has defied Holyrood chiefs in such a way.

A number of legal experts, including Lord Advocate James Wolffe, have since backed the SNP’s position.

The constitution, including a referendum on independence, is widely held to be reserved to Westminster.

Britain's Secretary of State for Exiting the European Union David Davis (right) reacts as he talks with the European Parliament's Brexit coordinator Guy Verhofstadt. Picture: Niklas Hallenniklas

But Tory MSP Donald Cameron has now warned the SNP could repeat the “wilful ignoring” of parliamentary authorities when it comes to legislating for a referendum re-run. He said the Scottish Government would cite the case of the UK Withdrawal from the European Union (Legal Continuity) (Scotland) which is being rushed through Holyrood this month. MSPs will vote on the measures today and it will be finally passed in a fortnight.

“We all know what’s likely to happen next,” Mr Cameron said. “Give it a few months, and the Nationalists will be back making the same arguments about the need for emergency legislation – but this time for their second independence referendum.

“The SNP has wilfully ignored the Presiding Officer’s ruling that its bill is beyond Holyrood’s powers, and it will happily do so again.

“The truth is that the wildcat legislation introduced this week by the SNP is simply a dry run to help it push a second independence referendum through parliament.

“Unlike Labour and the Liberal Democrats, the Scottish Conservatives will have no truck with the SNP’s games. We will oppose this irresponsible law-making.

“We will support a sensible deal on Brexit that brings more powers back to Scotland. And, above all, we will oppose any attempt by the SNP to impose a second independence referendum on voters.”

Nicola Sturgeon has said she still plans to stage a second independence referendum when the terms of Brexit become clear for Scots.

MSPs at Holyrood, where the SNP and pro-independence Greens have a majority, have already voted in favour of a second vote on leaving the UK. Ms Sturgeon says this gives her a mandate. It followed the Brexit vote which saw two-thirds of Scots vote to remain in the EU, while the weight of votes south of the Border swung the outcome in favour of leave.

But a spokesmen for the Scottish Government’s Brexit spokesman Michael Russell yesterday dismissed the Tory claims, insisting Edinburgh has been forced to draw up its own Brexit bill amid fears of a “power grab” on the Scottish Parliament by Westminster.

“This is a desperate Tory smokescreen to divert attention from their shambolic Brexit plans and the outrageous attack on the powers of our national Parliament by their Westminster colleagues,” the spokesman said.

“Protecting devolution is what this bill is about, and that is why it is supported by every party at Holyrood bar the Conservatives. The simple truth is this is a Tory party which now thinks it can do what it likes to Scotland and get away with it – but we are determined not to let them.”

Mr Russell will hold further talks with the UK government in London this week but indicated yesterday that he was not a particularly confident of any deal being reached on Westminster’s EU Withdrawal Bill. The dispute centres on 25 areas of responsibility which are being repatriated from Brussels after Brexit. The SNP says they are devolved and belong at Holyrood, but Westminster is proposing to retain them to create “common frameworks” which, it is claimed, are necessary to protect the integrity of the UK internal market. A UK government source said that Westminster is unlikely to compromise further.

SNP using Brexit showdown with Holyrood as '˜dry run' for indyref2