An independent Scotland would have to find up to £300 billion to prop up its own currency, the country’s most eminent macroeconomist has warned as Nicola Sturgeon prepares to unveil her new economic blueprint for separation.

Professor Ronald MacDonald, research professor of macroeconomics and international finance at Glasgow University’s Adam Smith Business School, said tens of billions of pounds in foreign exchange reserves would have to be raised to protect the currency from economic shocks and speculators.

Ms Sturgeon confirmed she had received the SNP’s Sustainable Growth Commission report, to be published on Friday, and plans to hold a series of meetings over the summer to discuss its recommendations before taking a “formal view”

It has been reported that the 354-page document will recommend that the pound be used on an unofficial basis immediately after independence before moving to a new currency pegged to sterling.

But Prof MacDonald, who is a monetary advisor to the IMF, told the Telegraph this would mean “massive” spending cuts, tax increases or both as Scotland’s share of the Bank of England’s reserves would not nearly cover the cost.

He warned that pegging the currency to sterling was a particularly “bad idea”, as this would require a far higher level of reserves – potentially hundreds of billions of pounds - to defend it from market attack or if Scotland’s economy performed poorly relative to the remainder of the UK’s.