Scottish secretary Michael Moore has told MPs that his talks with Alex Salmond over the date and precise question of the independence referendum have barely advanced at all.
There appears to be deadlock over when the vote should be held, with the coalition believing it could happen as early as September 2013, "without cutting any corners."
Salmond wants it to happen in the autumn of 2014, but Moore told MPs on the Scottish affairs committee on Wednesday afternoon: "I have not seen the knock out argument for why this referendum needs to be held back as long as is proposed."
At a meeting to update MPs on the discussions between Moore and Salmond earlier in the week, ministers also revealed why they were opposed to the SNP's plan to allow 16 and 17 year-olds to vote in the referendum.
Scottish Office minister David Mundell said it would rely on parents registering their teenagers as people likely to turn 18 within the following year or so: "Perhaps that is something that middle class parents might be proactive in doing. But not every parent or household would put their son or daughter on to the electoral register."
His statement is likely to annoy the Lib Dems, who are in favour of 16 and 17 year-olds voting in all elections. In fact Lib Dem MP Jo Swinson is holding an event in Parliament next week in support of the campaign group Votes at 16.
But Moore, himself a Lib Dem, also explained why the coalition was opposed to putting an additional question for greater devolution on the referendum ballot paper.
The government's principal objection is it could produce a scenario where a majority of scots favoured both independence and greater devolution, so-called "devomax".
What would happen if 70 percent of Scots voted for Devomax and 51 percent voted for independence, Moore asked, suggesting that the SNP believed in such an outcome there would be independence.
Moore also rejected calls for EU citizens living in Scotland to be banned from voting in the referendum, saying there was "no groundswell" for taking such action.
He claimed that the Scottish government needed to spell out their proposals for key policy areas ahead of the referendum, particularly on defence, including more detail on the future of the nuclear submarines, and the jobs that might be lost in aerospace.
Moore went on to say there had been suggestions that any Army regiment with the word 'Scot' or 'Scottish' in it would form part of a separated defence force. Some of these are actually not based in Scotland.
"We are deeply integrated into the whole UK defence establishment," Moore added, before saying many Scottish business leaders had told him the uncertainty was damaging confidence.
"Day and day they wake up and they get on with their business. The have concerns about banking, the markets and the Eurozone. On this decision, about when we have the referendum, it is entirely in politicians hands. We can get rid of this uncertainty by having it as early as possible."
SNP Constitutional Affairs spokesperson Pete Wishart MP said: “16 and 17 year olds already play a part in our society. They should be able to have their say over Scotland’s future. Attaching strings to Scotland’s referendum is simply not acceptable. The referendum should be decided by the Scottish people and the Scottish parliament.
“Penalising those 16 and 17 year olds who will be looking to the future of their country in an attempt to attack the SNP is just another sign of how badly the Tories, Lib Dems and now Labour are misreading the Scottish people.
It is grossly unfair those aged 16 and 17 are able to play a major part in our society, to pay taxes, join the armed forces, consent to marriage but under UK Government plans will not be barred from making democratic decisions about their own future.”