Former Labour chancellor Alistair Darling appeared to have Scotland’s First Minister on the ropes for much of the referendum debate, particularly on the prospect of a currency union.

Alex Salmond refused to set out a “plan B” if Scotland were unable to keep the pound during the pair’s first TV clash on Tuesday night.

Mr Darling jibed that the First Minister was the only person who thought sharing the pound was a realistic option.

“I want you to contemplate for one moment that you might be wrong,” he said.

Mr Darling said all eight-year-olds could name a country’s capital and currency — but the Yes campaign could not say for sure what money would be circulating in Scotland.

Accusing Mr Salmond of “stupidity on stilts,” he joked that Scotland could use the rouble or dollar.

But the First Minister shot back that Mr Darling had not done well with financial markets when he was chancellor at the time of the credit crunch.

Mr Salmond also attacked the No campaign for bringing forward “Project Fear” in a bid to win the referendum battle.