Danny Alexander has rejected claims by independence campaigners that he would be prepared to bargain on currency in the event of a Yes vote.
The chief secretary to the Treasury used a speech in Edinburgh yesterday to deny claims that the rejection of a monetary union was a tactical move.
The Scottish Government wants an agreement to formally share the pound, with the Bank of England acting as lender of last resort in the event of another banking crisis.
However, Chancellor George Osborne has ruled this out as too risky. He has the backing of Mr Alexander and Labour shadow chancellor Ed Balls.
Earlier this week, Crawford Beveridge, chairman of the Scottish Government’s Fiscal Commission, told MSPs he thought the UK Government was bluffing.
But yesterday Mr Alexander told the National Association of Pension Funds: “I’ve seen some people suggest we are not serious about refusing a currency union.
“Our decision – taken in the best interests of Scotland and the rest of the UK – is final. No ifs, no buts. No matter how much of a racket they make – it isn’t going to change.”
Deputy First Minister Nicola Sturgeon said Mr Alexander should have used his speech to “to apologise to people the length and breadth of Scotland”.
“Just this week, we have seen an independent report warn of a ‘humanitarian crisis’ in Scotland, with almost a million people in poverty as a direct result of those Tory-Lib Dem policies,” she said.
Katja Hall, Confederation of British Industry chief policy director, said: “The Scottish Government must outline its Plan B for the currency so that businesses and consumers are fully aware of the implications of independence.”