Passport controls would be introduced at Gretna and Berwick to restrict the movement of people into England if Scotland voted for independence, the Westminster government has warned.

Stricter regulations on travel between the UK and Ireland, the Isle of Man and the Channel Islands are due to take effect from 2014. Labour has said these would cover Scotland if Scots give their backing to separatism in a referendum next year.

The Scottish National party has long denied independence would lead to border controls that would make foreigners of English family members. Alex Salmond, the first minister, has said the common travel area that guarantees freedom of movement for Irish and British citizens would apply to Scotland.

However, Labour ministers fear a separate Scotland would be a “back door” for immigration into England. “It’s not just about following the new legislation through to its logical conclusion,” said a government source. “The other side of the story is

the open-doors policy that the SNP would have on immigration and asylum seekers. Other EU countries would go bananas and demand that Britain secured its border.”

Anne McGuire, the former Scotland Office minister, said: “This is the reality of a Scotland completely separate from the UK.”

John Curtice, professor mof politics at Strathclyde University, said: “Just as in the case of Ireland, it seems we can no longer presume that the government in London would be willing to dispense with passport controls. The stakes in the independence debate have been significantly raised.”

A spokesman for Salmond accused Labour of scaremongering and said: “This has no implications at all for the case for Scotland becoming an independent and equal country.”

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