Tories have accused the Scottish Government of being reckless by “overstating” the likely income from oil and gas.
Party leader Ruth Davidson criticised the figures, which are frequently used to support the case for independence.
She spoke out at First Minister’s Questions one day after Chancellor George Osborne said anticipated tax receipts from the North Sea have been revised down by the Office for Budget Responsibility (OBR).
The body now forecasts receipts will fall by almost 50% in four years, going from £6.1 billion in 2012-13 to £3.2 billion in 2016-17.
Mr Osborne, making his final Budget speech before the referendum, said the drop shows how “precarious” an independent Scotland’s finances would be.
Miss Davidson criticised Scottish Government projections, which she said go as high as £7.9 billion.
“The First Minister wildly overstated the case last year, he overstated the case for this year,” she said. “Why should we gamble the future of funding of our hospitals and schools on a man with such a track record?”
Mr Salmond stands by the figures, complaining that the OBR changes its mind every six months.
But Miss Davidson said oil is already trading at a lower price per barrel than the Scottish Government predicts.
“More than double than the recent projections doesn’t sound like being cautious to me, it sounds downright reckless,” she said.
“It’s now been over a year since the First Minister dashed out his dodgy oil figures in an analytical bulletin.
“He promised us regular updates but so far we’ve not had any. So when will the First Minister update his figures? And does he accept he will have to revise them down?”
Mr Salmond said the Government figures are based on oil at 113 US dollars a barrel, compared with other predictions going as high as 140 US dollars by the end of the decade.
“There’s a reasonable case to be made that this is not an overambitious forecast but a rather sensible one,” he said.
Production is likely to increase because of increased investment, he added.
“Given the evidence of the last 40 years, I think people are more likely to believe a Scottish Government forecast and estimations of Scottish natural resources than a Tory Party who have pocketed £300 billion of Scottish resources over the last 40 years,” he said.
