The Liberal Democrat Cabinet member dismissed Alex Salmond’s claims that Westminster’s politicians were “bullying” the Scottish Government by ruling out a currency union if there is a Yes vote in September’s referendum.
And the Scottish minister backed pop veteran David Bowie’s high profile intervention in the independence debate, saying celebrities could provide “inspirational leadership” to campaigns.
Bowie used his Brit Awards acceptance speech - delivered by supermodel Kate Moss - to plead with Scotland to stay in the union.
Mr Alexander said: “David Bowie’s call sparked strong reactions on both sides of an ever more passionate debate. He was attacked for being a ‘celebrity’, being English and not living in the UK.
“Even the hostile reaction to him posed some interesting questions and in part explains why this issue is now the subject of intense debate across the UK and not just in Scotland.
“Yes, the most important people in all of this are we who live in Scotland - it is our votes that will make the decision, one that will profoundly affect everyone in the UK.
“And why shouldn’t a ‘celebrity’ have a view and express it? Why shouldn’t an Englishwoman have a view on an issue that will change the country she lives in, too?
“Come to that, why should we be surprised that Brits living abroad have a view on the referendum? Celebrities can bring inspirational leadership to a campaign. Who could ever forget Joanna Lumley’s crusade for the Gurkhas?”
But he said that people were more important in the campaign than celebrities “however well-intentioned” they were.
Mr Alexander said: “What matters to me is what’s best for Scotland, and I want everyone to understand the economic risks, dangers, and huge uncertainties inherent in Mr Salmond’s leap in the dark.
“The facts and the economics emphatically do matter. The evidence convincingly shows that the future of Scotland will be most secure in the United Kingdom.
“It also shows that going it alone as a new independent state is fraught with risk.
“To have any chance of success, an independent Scotland would require a sound, carefully considered economic plan based on a solid currency.
“The omens are not good. The SNP has failed to come up with a ‘currency Plan B’ even though everyone now knows keeping the pound is not an option.”
He said Mr Salmond’s “threat” to renege on honouring Scotland’s share of UK debt in response to not being allowed a currency union was “immensely destructive”.
“If the first act of a new state was a default on its debt, this would create a huge leap in interest rates - which would have a serious negative impact on investment, jobs and prosperity,” he said.
“This is not bullying - it’s reality. These things would have a direct, profound impact on Scottish families and businesses.”
He repeated his warning that any default could result in the money markets taking fright, potentially hitting Scottish homeowners with £5,200 higher mortgages.