THE amount of recoverable oil in the North Sea could be less than half the SNP’s projections ahead of the independence referendum, a Scottish Government-appointed energy adviser has said.

Professor Alex Kemp said around 11 billion barrels could be extracted by 2050 compared to the 24bn barrels hailed by the SNP Government in its White Paper on independence.

Without sustained capital investment in North Sea the amount of recoverable oil could fall to just 5bn barrels, he said.

Oil prices have plummeted from over $100 a barrel to around $60 since 2014 and analysts predict they will remain “lower for longer”.

The lower price means hard to reach fields require more resources to exploit, and are not economically viable if costs outweigh profits.

Prof Kemp, professor of petroleum economics at Aberdeen University and a member of Nicola Sturgeon's Scottish Energy Advisory Board, said: “The very large unexploited potential indicates both the challenges and opportunities facing the industry.

“It is clear that a combination of further productivity improvements and oil and gas price increases can make a major difference to the overall economic recovery from the UK Continental Shelf.

“However, development of the unexploited potential would also greatly enhance the fortunes of the supply chain.”

He added: “If productivity can be significantly enhanced the economic recovery from the province can be greatly increased and the supply chain can benefit from a greatly expanded market.

“But if these productivity improvements are not achieved the prospect with ‘lower for longer’ oil prices is long term decline at a brisk pace.”

Tory finance spokesman Murdo Fraser said: “This is a significantly lower estimate than anything the SNP said, which casts more doubt on the Nationalists’ integrity during the 2014 campaign.”

An SNP spokesman said: “Instead of rejoicing in the downturn affecting the North Sea oil industry and the jobs affected by it, the Scottish Tories should be lobbying for support for the industry.”