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
An unsettled weekend in store for many
Four Arab nations that cut ties with Qatar over its alleged support for Islamist groups have handed their neighbour a 13-point list.
The father-of-four from Cardiff with appear in court this afternoon charged with terrorism-related murder and attempted murder.