Chancellor George Osborne has compared voting for independence to buying something from “someone who refuses to tell you the price”.
The Conservative minister’s attack on the SNP came amid an ongoing row over the costs of independence.
Finance Secretary John Swinney hit back, saying Scots “can’t trust a word” that comes from the Treasury.
He called on Mr Osborne to apologise over an academic’s claims that his work was “badly misrepresented” in a Westminster report this week on the cost of setting-up new bodies in an independent Scotland.
The pro-UK parties have challenged Scottish ministers to produce their own figure for the cost of going it alone, in the wake of the criticism of the Treasury report from London School of Economics professor Patrick Dunleavy.
In an article, Mr Osborne wrote: “Those who want a separate Scotland must explain how it would work and what the price would be.
“The first minister of Scotland and the Scottish Government refuse to be open with people about its real risks and costs.
“In an interview yesterday, the cabinet secretary for finance, employment and sustainable growth for the Scottish government was asked 11 times to say what would be the cost of setting up a separate Scottish state.
“He couldn’t or wouldn’t say. Why would you buy anything from someone who refuses to tell you the price?”
Mr Swinney responded, saying: “The very last person who should be trying to lecture Scotland is a Tory chancellor like George Osborne.
“Because the fact is that Scotland is already doing better than the rest of the UK when it comes to getting people into work.
“How much more we could achieve with the full economic powers of independence?
“The fact is we now know we can’t trust a word the Treasury says.
“George Osborne should be apologising after his department made up figures about the costs of an independent Scotland which have been disowned by the expert they were quoting.”