First Minister Alex Salmond has been accused of living in a fantasy world over issues such as whether an independent Scotland would retain its membership of the European Union.
He came under fire at Holyrood from all three main opposition leaders for the Scottish Government's stance on the EU membership issue.
The joint attack came in the wake of comments from Jose Barroso, president of the European Commission, who said it is "obvious" that a newly independent state would need to apply for membership.
The Scottish Government argues that could be negotiated from within the UK, an EU member state, after a Yes vote but before formal independence.
Unionists say Scotland would be left outside the EU until it was reaccepted, potentially forcing the country to adopt the euro currency and join the Schengen free-travel area, putting it at odds with England.
Labour leader Johann Lamont hit out at the "fantasy world the First Minister now inhabits". She claimed that Mr Salmond, his Deputy First Minister Nicola Sturgeon and Finance Secretary John Swinney are "misleading Scotland" about what would happen if it was to become independent.
"The man in charge of the European Commission, Jose Manuel Barroso, has told the BBC if there is a new state, of course that state has to apply for membership," Ms Lamont told the SNP leader. What part of that statement does the First Minister not understand?"
Mr Salmond told her: "The Scottish National Party Government has never argued we wouldn't have to negotiate our position in terms of the European Union. It's never been our position there would not be negotiations. The point is, negotiations would be held from within the context of the European Union."
He insisted that "no serious person actually believes" that if Scotland left the UK, it would be excluded from the EU.
He went on to highlight Scotland's resources, including North Sea oil and gas and the country's renewable energy, and said: "It's not just in the interests of Scotland to be a member of the European Union. It's overwhelmingly in the interests of the European Union to have Scotland as a member."