The poorest people stand to lose the most if an independent Scotland loses the pound, Ed Miliband has claimed, as the Labour leader piles on Alex Salmond after the debate.
Miliband challenged the SNP leader over his failure to come up with an answer to the issue of what Scotland would do if it went independent and could not keep the pound, when he debated Better Together campaign leader Alistair Darling.
Speaking ahead of an address to the Scottish Chambers of Commerce in Glasgow, Miliband said: "The currency that Scotland uses is crucial for Scotland's future.
"Nobody claiming to be a social democrat who cares about Scottish pensioners, Scottish families and Scottish businesses should dare take this risk without a currency plan.
"If you care about social justice in our country, you can't leave the economics to guesswork."
He added: "Those at the top can move their money across the border and keep the pound.
"We know that the people who would stand to lose most from making this decision are those who have the least.
"It would be working people, small businesses across Scotland who would be left to deal with the consequences."
He added: "I want business and families to have the certainty of the pound. But I can't support a eurozone-style currency union.
"We did not join the eurozone for clear and correct economic reasons.
"It is for the same reasons the rest of the UK should not enter into a currency union with an independent Scotland.
"And that's why, as prime minister, I couldn't agree to a currency union."
Speaking after an address to the Scottish Chambers of Commerce in Glasgow today, Miliband said the risks to the UK of sharing the pound with an independent Scotland would outweigh the benefits of cutting the UK national debt or preventing cross-border transaction costs.
He said: "40% of the UK's trade is with the euro area and 10% of the rest of the UK's trade is with Scotland.
"So, we're not about to join the euro because it's 40%, so therefore you have got to make a judgment about whether the currency union makes sense or doesn't make sense.
"Of course you want to avoid the transaction costs, which is one of the reasons we want the UK to stay together.
"But I'm afraid the cost of a currency union without political union, without a fiscal union, without banking union, are costs that will be too high for the UK."
Former SNP leader Gordon Wilson has called on Salmond to provide voters with more information on currency options, stating that "bold assertions are not enough".
He said: "The common-sense default position is that Scotland would continue to use the pound sterling, which is an international convertible currency.
"London could do nothing to stop Scotland from doing so. It is surprising Alex did not spell this out.
"He does not have to abandon his first preference of using the pound. He needs to explain the options simply."
SNP Treasury spokesman Stewart Hosie said: "The No campaign's scaremongering on the pound is crumbling."
He said Miliband had "exposed the fundamental flaw in the No campaign's argument which is that they cannot say no to continuing to share our pound without saying that they would make voters in the rest of the UK pay debts that would otherwise be paid by an independent Scotland".
"I'm not hearing Ed Miliband or anyone else making that statement in London," he added.
"With a Yes vote we can use the economic powers of independence to further grow our financial sector and attract new business to Scotland - and to have an economic policy tailored to Scotland's needs, rather than London and the South East."