SCOTS would be offered tailored passports as part of a radical proposal to allow them to live and work on mainland Europe after Brexit.

Holyrood officials are currently studying a plan drawn up by academics to maintain decades-old freedom of movement between Scotland and the rest of the European Union, even if it is lost by England and Wales.

The passport plan has emerged on the first day of a new Herald series which will examine the central hazards resulting from UK's European divorce while identifying solutions that will enable Scotland to benefit in an entirely new constitutional landscape.

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In one key plan, experts believe a devolved Scotland could issue its own national insurance (NI) numbers and that these could be used to apply for jobs on the continent.

Academics also believe that the Scottish Government could grant special Scottish-only NI numbers to citizens from other EU nations who already live in Scotland or who wish to take up posts north of the border.

Professors Damian Chalmers of the London School of Economics and Anand Menon of King's College believe such NI numbers, combined with address information from the electoral roll, would form the basis of "documents additional to their passports which could serve to secure them free movement in the rest of the EU".

The two London professors believe that such arrangements could be transitional, either helping Scotland to a soft landing from Brexit or tiding the nation over to a referendum for independence within the EU.

Their idea is being considered by ministers looking for options both to enable Scots to continue to enjoy freedom of movement rights for which they voted in last June's election - and to keep Scotland in the EU single market, for goods, services and labour.

Insiders stress that the Scottish Government, desperate to mitigate against the predicted economic and social costs of leaving the EU, has an open mind and is ready to think about all sorts of different scenarios.

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Speaking ahead of a major Holyrood debate on keeping Scotland in the single market, a Scottish Government spokeswoman said: "This is one of a number of valuable contributions to the debate, and the specific recognition that Scotland will need a close continuing relationship with the EU is a welcome one."

She added: "This and the other similar contributions illustrate the range of options potentially open to Scotland and the UK as a whole, and will inform our thinking as we prepare to publish specific proposals on maintaining Scotland’s place in Europe, including our continued place in the single market."

The Chalmers-Menon proposal was detailed in a position paper, widely shared in government circles, by two Scottish experts, Nina Miller Westoby of Glasgow University and Jo Shaw of Edinburgh.

The experts described continued free movement in Scotland after Brexit as "more plausible than at first blush".

They wrote: "Increasingly immigration control is taking place within the UK, in situ, for example by landlords obliged to confirm residence status before renting property, rather than traditional immigration control at the border, and this may be a means in which a differentiated immigration approach is developed.

"An example that has been mooted by Chalmers and Menon amongst others proposes that the Scottish Parliament become responsible for the issue of NI numbers and thereby develop a system where NI numbers are granted to EU and European Economic Area citizens which are only valid in Scotland."

Such a scheme may mean devolving control over wider migration from London to Edinburgh. UK ministers, including Scottish Secretary David Mundell, have already said they would rule this out.

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Such a stance, however, comes long before the start of what are likely to be multi-layer talks between London, Brussels and Edinburgh.

Business leaders and economists are looking for any way to keep a supply of foreign workers for the economy.

David Bell, of Stirling University, has warned that cutting off Scottish access to overseas labour would hurt key industries such as fishing, agriculture and higher education.

He said: "Scotland’s economy does not have a particularly strong export record: reducing its access to foreign workers and their expertise will make it even more difficult to expand its external trade."

Some experts are sceptical about the chances of the British Government giving up control of immigration, even though such powers are devolved in other states, such as Canada.

Kirsty Hughes is the EU expert who first mooted ways for Scotland to keep some of the advantages of EU membership after Brexit without pursuing independence.

However, she now believes that a separate deal on migration and freedom of movement is "highly unlikely" within the union. She said: "If Scotland wants either just migration policy and free movement or the whole single market shebang, how could Prime Minister Theresa May agree to that before knowing what the UK-EU deal was?"

She added: "And if by any chance the EU was ready to let Scotland be in the single market, it would want too to understand how that would mesh with the rest of the UK having a different deal when it has no border with Scotland."

So any Scottish deal, she said, would have to wait for the London-Brussels one.