Alex Salmond has sugested Scotland could become independent even if more people vote to preserve the union than to break up the United Kingdom, it has been reported.
Under the referendum plans Scots would be given two options, one on full independence and one that would save the union but transfer tax powers to Holyrood - known as "devolution max".
The Scottish first minister has indicated that he will encourage people to vote 'Yes' to both questions, opening the door to independence even if more people vote to preserve the union.
The SNP has suggested that a simple majority in favour of independence would be enough to justify breaking up the UK, even if more people vote for the increased powers option.
Westminster politicians have stepped up their war of words with Salmond as the prospect of a referendum draws nearer.
Labour MP Tom Harris, a candidate for the leadership of the Labour Party in Scotland, accused Salmond of attempting constitutional "jiggery-pokery".
Speaking in the Commons on Tuesday evening he said: "It is of the utmost importance that the result of any referendum cannot be second-guessed, misinterpreted, reinterpreted or undermined. It must not be ambiguous," he said.
And he attacked the "devolution max" option, or the “I Can’t Believe It’s Not Independence” as he branded it, as unworkable as it would affect fundamentally the way in which whole of the United Kingdom, not just Scotland, was governed
Scotland minister David Mundell also dismissed the idea of full fiscal autonomy for Scotland as a "fallacy".
"There is no third way. The only choice is between separatism and remaining in the United Kingdom." he said.
"What the people of Scotland need now is not vulgar triumphalism from Mr Salmond and glossy brochures from the SNP, but facts, evidence and answers."
While Lib Dem Cabinet Office Minister Lord Wallace of Saltaire told the House of Lords on Tuesday that Salmond was a "very provocative populist" who liked provoking the Westminster government.