First Minister Alex Salmond has challenged his unionist opponents to test their plans for Scottish constitutional reform in a public vote.
The Scottish Government aims to stage a referendum in 2010 on whether Scotland should become independent.
Mr Salmond suggested it could include two other options - more powers for the Scottish Parliament or no change in the present set-up.
The Tories dismissed the plan as "the wild words of a panicking man".
Mr Salmond made the suggestion as he launched the latest phase of his "national conversation" on Scotland's constitutional future, published last year in a white paper which strongly favoured independence.
Speaking at an event in Edinburgh which aims to engage a wide variety of civic groups in the debate, he said voting in the government's referendum could be carried out on a PR system of one-two-three preferences - the system now used in council elections.
However, the SNP's political rivals - who have just launched their own independent review of devolution which will not consider independence - pointed out the minority Holyrood administration did not have enough parliamentary support to stage a referendum.
"I am happy to test support for enhanced devolution, along with support for independence for Scotland," Mr Salmond told the audience, comprising business groups, unions and education representatives.
"And I say to those who oppose the restoration of Scottish independence that just as I respect absolutely their right to hold that view, so in return I feel able to require of them a clear alternative which can be put onto a ballot paper and held up to public scrutiny and be available for a decision by the Scottish people."
The event came a day after the launch by Scotland's pro-Union parties of the independent constitutional commission to review devolution.
Mr Salmond has called on the commission to alter its remit to look at independence.
Scottish Conservative leader Annabel Goldie said the "absurd" suggestion of an independence referendum under the single transferable vote system showed the government was clutching at straws.
She said: "This is tripe - the wild words of a panicking man. You don't have a referendum to preserve the status quo - devolution is the status quo."
Scottish Labour leader Wendy Alexander described Mr Salmond's suggestion as a "back of an envelope" approach to considering Scotland's future.
"Alex Salmond must be delusional if he thinks that Scotland will be happy to accept independence by the back door," she added.
Scottish Liberal Democrat leader Nicol Stephen, who has dismissed a multi-question referendum as a "red herring", added: "The SNP continues to attempt to drag an unwilling Scotland towards independence.
"For a party which chants the rhetoric of democracy at every opportunity, it is profoundly undemocratic to engage in this costly, taxpayer-funded persuasion exercise without any parliamentary mandate."