Alex Salmond has failed to guarantee an independent Scotland would keep the pound.
Labour said the First Minister appears to be a “fool” who does not have a plan B for the currency if he cannot strike a deal to keep the pound in the event of a Yes vote.
The fall-out came on Thursday, the day the Scottish independence referendum passed its final parliamentary stage at Holyrood.
Party leader Johann Lamont made the claim at First Minister’s Questions after it was reported that the Scottish Government’s White Paper on independence will not include a pledge to retain sterling in a currency union with the rest of the UK should next year’s referendum result in a Yes vote.
Colin McKay, head of the Scottish Government’s strategy unit, was reported to have said: “We cannot assert as an a priori fact that we can achieve a currency union with the UK, but we can set out why we think it is the best option.”
Mr Salmond said: “The essence of the argument for the sterling area is it is in Scotland’s interest because England is our biggest customer, and it is in England’s interest because Scotland is England’s second-biggest customer,” he said.
However, Ms Lamont hit back, telling him: “Alistair Darling (who heads the No campaign) said Mr Salmond must have a hidden fall-back option because ‘no one but a fool would go into a negotiation if they haven’t got a plan B’.”
“It would seem we have a fool here who has no plan B on the currency.”