Scottish independence would be less "viable" if the UK exits the EU's Single Market, according to leading academics.

Leaving would create the need for a hard border between an independent Scotland and England, a new report 'How the United Kingdom might leave the European Union', by the UK in a Changing Europe group for the Political Studies Association, says.

The First Minister has called for Scotland to get a separate deal to stay in the Single Market.

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The Scottish Government's blueprint for a special post-Brexit deal between Scotland and the EU is due to be published by the end of the year.

It will explain how minister's believe the country could maintain membership of the Single Market even if the rest of the UK leaves.

But experts suggested that the case for independence would be hit unless all of the UK remains in the Single Market.

They said that the idea of "independence-in-Europe which the SNP has pursued for some 30 years is based on the logic that with both Scotland and the UK in the EU, trade and border issues between the two would be unproblematic.

“But with Scotland in and the UK out of the EU, there would be a hard border between the two.”

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They add that polls do not suggest that voters in Scotland would be ready to give up the UK market in return for access to the European one.

"If the UK were to negotiate access to the Single Market, however, that would make Scottish independence more viable," they find.

The report also warns that Brexit will have a “big impact” on devolution.

What form that will take remains to be seen, the academics say.

One possible scenario is a ‘re-centralisation’ of the UK.

On the other hand, however, they could be further decentralisation with areas currently under EU control being devolved to Holyrood, Stormont and Cardiff Bay.

They warn, however: “In either case, the process will be difficult and controversial."

The report also warns that Brexit will place enormous pressures on Westminster, government officials, the courts and the British constitution.

The civil service faces its “biggest ever challenge,” they say.

Read more: Former minister Alex Neil to join Brexit 'awkward squad' as SNP divisions spill into open

Professor Anand Menon, the director of the UK in a Changing Europe project, said: “Brexit has the potential to test the UK’s constitutional settlement, legal framework, political process and bureaucratic capacities to their limits – and possibly beyond.”

Scottish Labour Europe spokesperson Lewis Macdonald said: “Labour supports the Scottish Government’s attempts to get the best deal possible for Scotland but we all need more information on what is happening next, and what analysis the Scottish Government is getting on with."

The report was published as the credit ratings agency Moodys also warned that the UK's credit rating would be damaged if it lost ‘”core elements" of its access to the Single Market.