A separate Scottish deal on EU membership would result in the fracturing of the UK domestic market, with "significant detriment" to the economy north of the border, according to an advisory group set up by the Scottish Conservatives.

Its report concludes a differentiated deal, as proposed by the Scottish Government, is neither deliverable nor in the country's self-interest.

"Such a deal would break our integrated domestic UK market, whose economic importance to Scotland is paramount," the report concludes.

First Minister Nicola Sturgeon has put forward proposals for a "differentiated deal" for Scotland in the wake of the Brexit vote. Such a proposal could see Scotland remain part of the European single market through membership of the European Economic Area.

An advisory body established by Scottish Conservative leader Ruth Davidson looked into the proposal and it has now published a paper on it, entitled Scotland's Trading Future.

The group concluded that unless the Scottish Government changes its position on immigration, it is "inevitable" that some level of internal UK border controls would have to be introduced.

It found that even in the absence of tariffs between Scotland and the rest of the UK, the flow of goods and services across the border would "inevitably be affected" by more restrictive controls.

There would also be a gradual "divergence" between Scotland and the rest of the UK as Scotland, through EU or EEA membership, was forced to adopt more EU regulations and laws, the panel said.

"It is pivotal that all parts of the UK come together and present a united front, so that efforts are focused on getting the best possible deal," the report concluded.

"We cannot see the self-interest in a so-called 'differentiated solution' for Scotland. It would have the effect of damaging the economy and reducing growth in Scotland."

Ms Davidson said: "The report makes it very clear: none of the challenges posed by Brexit are answered by weakening or breaking up our own union of nations.

"This report makes a compelling argument that as we embark on our departure from the EU, the protection of our own union is vital to Scotland's self-interest."

A spokesman for Scotland's SNP Brexit minister Michael Russell said: "It's hardly a surprise that a Tory commission including a heavy dose of Tory politicians backs the Tory Government's plan to drag Scotland out of Europe against its will - despite Ruth Davidson's backing for our continued place in the single market immediately after the Brexit vote.

"Our plans are specifically designed to ensure that Scotland does not have to choose between trading with the UK and trading with Europe, whose market is around eight times bigger than the UK's alone.

"Our proposals have been widely welcomed by a broad range of leading figures from business, academia, trade unions and wider civic Scotland, and represent a significant compromise on our part - a compromise which so far has not at all been matched by the UK Government."