Nicola Sturgeon has reiterated the case that an independent Scotland would be financially secure enough to go it alone, a day after an influential thinktank warned the nation could face a decade of austerity if it split the union.

Sturgeon, Scottish deputy first minister, said she believes the economy "is at the heart of the debate" ahead of a 2014 referendum on independence from the UK.

The National Institute of Economic and Social Research (NIESR) said in order to meet EU debt-to-GDP rules, as well as maintain borrowing costs at sustainable levels, an independent Scotland would need its own currency and annual fiscal tightening of 5.4% over ten years.

"My argument is that Scotland can more than afford to be independent. We are one of the wealthiest countries in the world. We more than pay our way," Sturgeon said on BBC Radio 4's Today programme.

"If you take each and every one of the past 30 years, we've generated more tax per head than the UK as a whole."

She added: "There's no question Scotland can be independent. The question is should we be independent."

The NIESR report on Scotland's currency options said central to the independence question is UK public debt and how much the nation would inherit. It said Scottish debt could be written down in exchange for oil revenues for the rest of the UK from the North Sea field.

Sturgeon claimed that however the UK public debt would be divided in the wake of an independent Scotland, her nation would have a lower debt-to-GDP ratio than the UK.

Alex Salmond, Scotland's first minister and leader of the Scottish National Party (SNP), has said they would keep sterling as the currency if the nation becomes independent.

When pressed on this given the NIESR research that suggests Scotland needs its own currency and central bank to ensure financial stability if independent, Sturgeon defended keeping sterling.

She said the SNP had commissioned experts to look into the scenarios and they concluded that keeping the British pound was the best option for not just Scotland, but also the rest of the UK.

Alastair Darling, the Labour MP and former chancellor who is leading the campaign to keep Scotland in the UK, hit back at Sturgeon.

"We are part of one of the oldest social and political unions in the world. Yes, we have had our ups and downs, but actually it has benefitted all four parts of the United Kingdom," he said on the same programme.

"What the nationalists are doing is trying to run this argument that everything will change, but then at the same time nothing will change.

"I think Scottish firms, therefore jobs, would suffer if we put a barrier between ourselves and, frankly, what the rest of our market is."