A majority of people are against the SNP's plan to keep sterling in the event of independence, according to a poll conducted by pro-Union campaigners.
Better Together, with polling company YouGov, asked more than 1,000 people what currency they want for Scotland, in or out of the UK.
The result suggests 56% want Scotland to remain in political union and keep the pound, compared with 17% supporting the SNP's position that Scotland should keep the currency but leave the UK. One in 10 people would prefer a Scottish currency, the poll suggests.
Better Together leader Alistair Darling, a Labour MP, said currency is one of the most important details in the referendum debate.
"A currency union means that the two countries involved, Scotland and the rest of the UK, would have to agree everything," he said on the day the SNP meets for its spring conference in Inverness.
"They would have to agree on their tax, on their spending, on their borrowing. In other words, Scotland's budget would have to be agreed by another country - that's not independence."
SNP MSP Annabelle Ewing said the polling questions were misleading.
"Scotland is stronger than the UK as a whole to the tune of £4.4 billion, and independence gives Scotland control of the fiscal levers to help build a prosperous economy and fair society. That is what independence is all about," she said.
"Mr Darling would do better do read the hugely detailed report of the Fiscal Commission Working Group, which sets out how a sterling zone would benefit both an independent Scotland and the rest of the UK.
"Governments in modern economies don't control interest rates, whether in the UK, eurozone, or United States."