Doubts over whether an independent Scotland could build up an oil fund to manage offshore tax revenue have been expressed by an academic think-tank.
The National Institute of Economic and Social Research (NIESR) took the view after looking at the likely share of debt and estimated income facing Scotland following a Yes vote.
The Scottish Government wants to set up an energy fund to “safeguard” the benefits of oil and gas production as an early priority.
A NIESR research paper compares the past five-year average of £9 billion and a projected revenue of £3.2bn in 2016-17, the year Scotland would officially be independent according to the SNP timetable.
“Tax revenues from offshore oil and gas are notoriously volatile,” the NIESR paper states. “Revenues from oil and gas fell by almost one half between 2011-12 and 2012-13 to £5.3bn.”
Scottish Conservative MSP Alex Johnstone said: “This report is a severe blow to the credibility of so many of the SNP’s plans.”
But a Scottish Government spokeswoman said: “Scotland is a wealthy country with an economy that would be among the top 20 in the world in terms of GDP per capita as an independent country.”