OIL forecasts used by the Scottish Government to support its case for independence are "aspirational" and unlikely to be realised, a senior industry figure has warned.

Former CBI Scotland chairman Melfort Campbell, who chaired a review of North Sea taxation and regulation for the Scottish Government backed comments by Sir Ian Wood, who this week accused the Scottish Government of over-estimating remaining oil reserves by at least 40 per cent.

The oil tycoon said the "best outcome" would be to recover a further 15 to 16.5 billion barrels in the coming decades.

However Alex Salmond defended his government's use of the industry's maximum estimate of future reserves, 24 billion barrels.

In a statement yesterday, Mr Campbell said expert reports had agreed that between 12 billion and 24 billion barrels were recoverable from the North Sea.

But he added: "The 24 billion figure is the aspirational scenario - the ultimate prize that we could win if there is a radical review of the fiscal and regulatory regimes and improved stewardship of the North Sea.

"This figure takes account of present, potential and probable discoveries.

"However, as our report states, the UK North Sea is at a crossroads. With current uncertainty, ageing assets, spiralling costs and the challenges of improving production efficiency and attracting investment, we will be hard-pushed to achieve the mid-range scenario of around 15-16 billion let alone the holy grail of 24 billion barrels."

Labour's Douglas Alexander said: "It is becoming clear that the figures on which Alex Salmond bases his economic argument simply do not add up."

However, Mr Salmond's claims were supported by Aberdeen University oil economist Professor Alex Kemp, who said 24 billion barrels was a "plausible" forecast.