Chancellor George Osborne has insisted there is still an economic case for Scotland to stay within the United Kingdom.
Mr Osborne entered the independence debate during a visit to Glasgow, where he gave a speech to business leaders at the annual Confederation of British Industry (CBI) Scotland dinner.
He said there is more to Unionism than "wallowing in nostalgia".
Setting out his case for a No vote in late 2014, he accused Scotland's First Minister Alex Salmond of failing to provide a credible answer to his plan for a shared sterling currency union.
"Today the advocates of independence argue that Britain's value to Scotland is spent, that union is no longer in Scotland's economic interests and that those who continue to believe in Britain are wallowing in nostalgia," said Mr Osborne.
"I want to take this argument head-on. I make no apology for sharing all of the instinctive emotional attachment to Scotland's place within the UK. Our shared history and culture, distinct yet intertwined identities, a whole greater than the sum of its individual parts.
"In a world in which a separate, independent Scotland wished to pursue divergent economic policies, what mechanism could there be for the Bank of England to set monetary policy, as it does now, to suit conditions in both Scotland and the rest of the UK?
"If the Scottish Government cannot provide answers to these basic questions about Scotland's currency, then the Scottish people are entitled to ask this basic question in return: what path is the Scottish Government leading them down?"
A spokesman for Scottish Finance Secretary John Swinney said: "Scotland needs no lessons from a Tory Chancellor whose disastrous economic policies are threatening jobs and investment across this country.
"The uncertainty being caused to Scottish businesses is through Mr Osborne's policies and his Government's failure to invest in capital projects. "The cast-iron position is that an independent Scotland will keep the pound, a position that Scottish Secretary Michael Moore has agreed with."
The Press Association, photo by HM Treasury