A former head of the UK's financial regulator has questioned the Scottish Government's currency and financial plans for the country under independence.
Sir Howard Davies, a former chairman of the Financial Services Authority, said the SNP position to keep a central Bank of England and the pound is unclear.
"It's not obvious quite how a system with two separate finance ministries and one central bank would work," he told BBC Radio Scotland's Good Morning Scotland.
The comment follows a speech by Finance Secretary John Swinney on Monday in which he underlined the plan to keep a "sterling zone" and the UK regulatory framework if Scots vote for independence in 2014.
Sir Howard referred to the current European Union banking crisis, arguing that its central bank is not prepared to provide money without limit.
"Supposing the Bank of England looked again at a Scottish bank and said 'It's really in trouble, people would would want it to be rescued, but we're not going to rescue it unless we're indemnified'.
"Where would they look for that indemnity? It wouldn't be the UK Treasury, presumably the English Treasury — it would have to be the Scottish Treasury.
"I don't quite know how you can be a servant of two masters, in terms of two separate treasuries and one central bank. I can't think of an analogy where that's the case."
Mr Swinney described the SNP administration's plan to a business audience in Glasgow on Monday.
In his speech, he said: "A sterling zone will provide businesses both in Scotland and the rest of the UK with the certainty and stability for trade, investment and growth.
"And as the Bank of England takes on the role of regulator for UK financial services — a very sensible and long overdue position — retaining the pound will preserve the highly integrated UK financial services market.
"That framework is solid and substantial and I know that understanding our proposal is important to many of you in making your decisions about Scotland's future."
Deputy First Minister Nicola Sturgeon defended the position following Sir Howard's comments.
Asked how a Scottish institution would be bailed out, Ms Sturgeon told Good Morning Scotland: "We've covered this point previously. The Scottish Government, in that scenario, would pay the Bank of England to provide lender of last resort facilities for Scottish banks.
"The Scottish Government has made clear, the SNP's made clear, that an independent Scotland would remain within sterling."
The position is "eminently sensible", she said.
Scottish Liberal Democrat leader Willie Rennie said: "Howard Davies is right to question whether the Bank of England, controlled by the rest of the UK, would be willing to act as a lender of last resort for Scotland.
"It is increasingly clear that SNP plans to have one Bank of England controlled by two finance ministers from different countries, or the 'servant of two masters' as Mr Davies characterises it, would be a recipe for economic uncertainty.
"As former chairman of the FSA, he is an expert whose views carry considerable weight. Far from securing more control over Scotland's economy, separation would lead to less.
"Every time the SNP try to explain their policy on the pound, the more confused and muddled the issue becomes."
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