The UK Government's adviser on Scots law has raised concerns that independence will create uncertainty during negotiations on key issues such as currency.
Lord Wallace, Advocate General for Scotland, gave his view on SNP policy before a speech to the Institute of Chartered Accountants in Aberdeen.
"Their current preferred option, so it would seem, is to have a formal currency union with the rest of the UK, and that must involve negotiation," he said.
"And if there is a lesson from the current eurozone crisis it is that far from fiscal autonomy, a formal currency union requires more political and fiscal integration, not less.
"The contrast couldn't be more stark: a Yes vote for uncertainty pending negotiations with little or no guarantee of greater fiscal autonomy, pain for doubtful gain; or a No vote and the certainty we shall continue with the remarkably successful political and monetary union we've enjoyed for the last 300 years."
Lord Wallace, a Liberal Democrat peer, said the Scottish Government's position inevitably means there will be negotiations on issues such as currency and EU membership.
"That uncertainty, bad in itself for business, inconveniently gets in the way of the rosy picture they like to paint of an independent land flowing with milk and honey," he said.
Both issues, particularly EU membership, have dominated political debate at Holyrood in recent weeks.
