Labour claimed Alex Salmond's credibility was "fatally damaged" and demanded he make an emergency statement on the issue.
The Tories said that trust in the SNP administration has been "blown apart".
It comes after Deputy First Minister Nicola Sturgeon revealed that the Scottish Government had only now commissioned "specific legal advice" from its law officers on an independent Scotland's membership of the European Union.
Opposition politicians turned on Mr Salmond, saying that during an earlier television interview he appeared to say that he had already taken legal advice.
In March the BBC's Andrew Neil asked Mr Salmond directly if he sought advice on the question of Scotland's future in Europe. The First Minister told him: "We have, yes, in terms of the debate."
Mr Salmond appeared before Holyrood to insist that he was "talking about the issue of Scotland's EU membership in terms of general debate, and in terms of the many eminent legal opinions offered".
Labour's Paul Martin accused the First Minister of telling "barefaced lies".
Fellow Labour MSP Jackie Baillie has now demanded that Mr Salmond make an emergency statement to Holyrood as she too accused him of lying.
The Tories also went on the attack, arguing that the SNP leader misled the public.
The row erupted just hours after two MSPs quit the SNP because of its u-turn on Nato membership.
Ms Baillie told BBC Radio Scotland: "There is absolutely no doubt in my mind that the First Minister is guilty of lying on this issue.
"He's given the impression on several occasions now that this legal advice exists and it was greeted with some surprise yesterday when the Deputy First Minister said we haven't had any legal advice."
Tory deputy leader Jackson arlaw added: "Yesterday was a watershed in terms of the public's perception of the Government.
"Any fair-minded person is going to conclude the First Minister has been disingenuous with the truth."