The SNP has called for the publication of what it has described as a “secret” independence referendum poll which was commissioned by the UK government.
The nationalists believe the publicly-funded survey was buried as it showed a “surge” in support for independence.
Deputy Prime Minister Nick Clegg responded by saying the only poll that counted was the one on 18 September.
Voters in Scotland will be asked the “yes/no” question: “Should Scotland be an independent country?”
SNP MP Angus MacNeil claimed in the Commons on Tuesday that the opinion poll was commissioned from Ipsos/Mori at a cost to the taxpayer of £46,500,
He urged Mr Clegg to publish it.
The deputy prime minister told Mr MacNeil: “I’ve learnt to try and be a bit wary about opinion polls.
“The only poll that counts is the poll that’s going to happen on September 18 and I very much hope, and I think people even like myself who don’t have a vote, those of us south of the border, fervently hope the Scottish people will decide to remain part of the family of nations that makes up the United Kingdom.
“Because there is so much that we can do together that we simply cannot do apart and that’s very much the argument that I hope will prevail on September 18.”
The call for the poll to be published was repeated by the SNP’s Treasury spokesman, Stewart Hosie, on Wednesday – the day UK Chancellor George Osborne appears before the Scottish affairs committee at Westminster.
He said: “George Osborne must agree to publish this secret poll – which has been paid for by the taxpayer.
“We know the coalition have spent an eye watering £46,500 of public money on voting intentions in the referendum, and have now locked it up in a vault in Whitehall.”
The survey was revealed in a letter under the name Kelly Brown that was sent to a newspaper. The letter’s author claimed to work for Ipsos/Mori, and said the results of the poll had been “buried as it returned a result which showed the Yes vote was soaring”.
Ipsos/Mori has said that it does not employ anyone with the name Kelly Brown.
The UK Cabinet Office said it was not usual practice to publish “internal research”.
Mr Osborne will be joined by the Permanent Secretary at the Treasury, Sir Nicholas Macpherson, when he appears before the Scottish affairs committee.
The SNP is boycotting the committee, which is comprised of MPs from the three main pro-Union parties.
Earlier this year, Mr Osborne and the finance spokesmen for Labour and the Liberal Democrats ruled out a currency union between an independent Scotland and the rest of the UK.
At the same time, senior civil servant Sir Nicholas made his advice on the topic public.
The Scottish government said it wanted a monetary union with the rest of the UK in the event of a “Yes” vote in September’s referendum.
It believed that, regardless of what is said now by the three main UK parties, a deal would be struck if there was a vote in favour of independence.