Labour's Johann Lamont, Conservative Ruth Davidson and Liberal Democrat leader Willie Rennie have united to urge the First Minister to consider the idea.

The opposition chiefs argue the wording of a "clear, fair and simple" question should be determined by constitutional experts – not politicians. The wording they come up with for the referendum – which is likely to be held in autumn 2014 – would then have to be approved by the Electoral Commission.

Ms Lamont, Ms Davidson and Mr Rennie want to meet Alex Salmond next week to discuss the matter.

Ms Lamont said: "All the parties agree that a single question is what we want.

"We are now calling on Alex Salmond to join us to ensure the wording of it is clear, fair and simple – and most of all trusted by the Scottish people."

The Scottish Government has already said its preferred question is: "Do you agree that Scotland should be an independent country?"

A spokesman for Parliamentary Business Secretary Bruce Crawford said that while the Electoral Commission would advise on the referendum question, it would be for the Scottish Parliament to decide.