An independent Scotland would be "over-reliant" on oil and gas, according to the Conservatives.
Research by the Centre for Public Policy for Regions (CPPR) found that, excluding the extraction of North Sea oil and gas, in 2011 the Scottish economy grew at +0.5%, half the rate seen for the UK.
If North Sea economic activity were apportioned on a geographic basis then Scotland's GDP including oil and gas extraction is likely to have fallen by over 3% in 2011, the report said.
North Sea output fell "considerably" in 2011, with oil and gas production down 18% and 22% respectively, according to the study.
Scottish Conservative finance spokesman, Gavin Brown MSP, said: "A separate Scotland would be over-reliant on oil and gas.
"This can prove risky, particularly with the wild fluctuations in prices we have seen in recent years.
"At some point in the future it will run out and of course we will no longer be able to rely
on it at that stage.
"Furthermore, the SNP have failed to take into the account the billions needed to decommission the North Sea oilfields."
Scottish Labour said that Scotland is stronger working in partnership than in competition with its neighbours.
The party's finance spokesperson Ken Macintosh MSP said: "The reality is that if Scotland separated from the rest of the UK, we would have a very significant spending black hole and the economy would be in a more precarious position.
"The reason for that is simple: more money is spent in Scotland than is raised in Scotland, and has been for the last quarter of a century.
"What the SNP seem unable to acknowledge is that oil and gas are volatile and declining commodities, and that a separate Scotland would be less insulated from shifts in global commodity prices."
Finance Secretary John Swinney MSP said: "The fact is that the Scottish economy outperformed the UK as a whole in terms of GDP growth over the last two quarters of 2011 - and we have a higher employment rate and lower unemployment in Scotland compared to the position south of the Border.
"More than half of the value of North Sea oil and gas reserves have yet to be extracted - by definition 'exceptional' interruptions in output in 2011 do not reflect the future - and in any event this report is referring only to production rather than value. In the current year, 2011/12, North Sea revenues are forecast to surge to over £11bn.
"Scotland needs the full economic and financial powers of independence so that we can do even more to boost the economy and jobs."
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