An independent Scotland would be forced to write the rest of the UK a £143bn IOU for national debt, according to the National Institute of Economic and Social Research (NIESR).
The Scottish government would have to make annual payments representing the share of debt interest plus the maturing debt, the economic research unit said, with roughly £23bn due in the first year.
It said an independent Scotland would not have the resources to pay off the full share of debt: "Therefore, an IOU obligation would be created where the Scottish government would make annual payments to cover its share of debt interest plus the maturing debt.”
Given the rest of the UK would be exposed to the continuing national debt payments, there would be little incentive for the Bank of England to act as lender of last resort to Scottish-based institutions, it added.
An independent Scotland would also have a debt to GDP ratio of 86%, NIESR calculated, although this lower than the existing UK debt to GDP ratio of 88%.
NIESR has also criticised key policies of the pro-independence camp, including the possibility of building up an oil fund, as well as the prospect of a sterling currency union.
An independent Scotland in a formal monetary union would pay between 0.72% and 1.65% more than the UK for issuing ten-year bonds, according to the research group. Scotland has recently been granted the power to issue its own gilts.
However, a currency union could also leave Scotland as a “hostage to fortune”, it argued, with few positive historical examples of such cross-border fiscal agreements.
NIESR also questioned the viability of proposals to create an oil fund from the proceeds of offshore oil and gas revenues. “It is difficult to see how such an oil fund could be built up. In 2012-13, Scotland’s onshore fiscal deficit was 14% of its GDP," it said.
A report by BlackRock in March outlined major risks facing the Scottish financial services industry, including the continued uncertainty surrounding EU membership and regulation.
However, it also argued an independent Scotland could woo its industries, as they were the "grouse that lays the golden egg".
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