The Scottish First Minister has warned that rejecting a currency union with an independent Scotland would cost British businesses hundreds of millions of pounds.
During a whistle-stop trip to Edinburgh on Thursday, Chancellor George Osborne declared: "If Scotland walks away from the UK, it walks away from the UK pound."
Alex Salmond, the SNP leader, told Sky News that Mr Osborne was "bluffing".
"It's absolutely daft that a London Chancellor is putting that forward - he won't put it forward the day after the referendum," he said.
In a speech to business leaders in Aberdeen , Mr Salmond accused Mr Osborne of a "complete misrepresentation" of the situation.
He warned the transaction costs involved in having separate currencies could cost British businesses £500m.
"The Chancellor downplayed the disadvantages to the rest of the UK from a sterling zone," the First Minister said.
"I am publishing today an estimate of the transaction costs he, the Chancellor, would potentially impose on businesses in the rest of the UK if he tried to force Scotland into a different currency.
"They run to many hundreds of millions of pounds.
"This charge - let's call it the George Tax - this would be impossible to sell to English business, to be charged by their own Chancellor for the privilege of exporting goods to Scotland."
Following Mr Salmond's speech, the SNP issued a series of papers which outlined the cost of a separate Scottish currency to UK business.
A second paper challenged the No campaign's claim that a currency union would limit Scotland's economic independence.
Liberal Democrat MP Danny Alexander, the Treasury's Chief Secretary, told Sky News the British Government would hold its ground when it comes to a currency union.
"What we said last week was based on serious economic analysis which showed that currency union would be very bad for Scotland under independence, it would be bad for the rest of the UK too," he said.
"It's important that we be clear with people in Scotland that what the SNP is saying - that they could somehow make the rest of the UK enter into a currency union - is just wrong."
Mr Salmond is also facing renewed attack on the Scottish Government's hope to achieve smooth transition to full EU statehood.
Jose Manuel Barroso, president of the EU's ruling body, the European Commission, said Scottish membership would be "extremely difficult, if not impossible".
But in his speech Mr Salmond said that no EU member state has indicated it would seek to block Scottish membership.
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