Alex Salmond claims Danny Alexander has been "caught red-handed" with "scaremongering" claims about the impact of Scottish independence.
The SNP leader told the BBC the Treasury's calculations had been "blown to smithereens" by the same academic whose work underpins the British Government's analysis.
Professor Patrick Dunleavy of the London School of Economics said Treasury figures about the cost of setting up a new independent government were "bizarrely inaccurate".
Mr Salmond seized on Professor Dunleavy's words, saying: "We have the Chief Secretary to the Treasury left with no credibility whatsoever. He’s been caught red-handed engaged in a scaremongering campaign.”
More top news
A wintry start to the weekend
A teacher has died after being hit by a dislodged manhole cover which smashed through her windscreen.
A dog has been found with its paws frozen to the ground in a New York park after being chained to a tree.