SCOTLAND may have ditched the pound in favour of a new currency within 10 to 15 years, the Economy Secretary has suggested.

Keith Brown said it was impossible to tell what currency the country would be using in the next decade.

It comes as the SNP prepares to publish a long-awaited blueprint outlining how Scotland can go it alone, which is expected to back a gradual transition to a new currency.

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First Minister Nicola Sturgeon insisted the document would "restart the debate" on Scottish independence.

Mr Brown made the comments after he was questioned about plans for a Scottish National Investment Bank at Holyrood’s economy committee.

Scottish Conservative MSP Dean Lockhart asked: “Can you confirm that the Scottish National Investment Bank will continue to use Sterling as its currency over the next 10 to 15 years?”

Mr Brown replied: “I think that would be the person that's got the job of trying to establish certainty going forward to a 15 year period – nobody else can do that.

“Who knows what changes are going to happen over the course of that time? That's the currency they're going to work in, sure, when they're started, but beyond that who can say what currency changes are going to make. I certainly can't – I'm not a currency expert.”

The SNP’s Growth Commission, due to be published on Friday, will make recommendations on the monetary policy for an independent Scotland.

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Reports indicate it will support a gradual transition on currency, with Scotland continuing to use the pound before switching to a new currency that would initially be pegged to Sterling.

Mr Brown, who is the favourite in the contest to become deputy leader of the SNP, previously said he wants to help get the party ready for “any future referendums”.

He said a second independence referendum could be held "in 12 months or two years".