According to a YouGov poll, only a third of respondents, 33 per cent, believed the main pro-UK parties would increase the Scottish Parliament’s powers while almost half, 47 per cent, were not convinced.
The findings have been seized on by the SNP, which commissioned the poll, as evidence that a key part of the Better Together campaign strategy against independence is flawed.
Conservative Prime Minister David Cameron last year promised that there would be further devolution, while Scottish Tory leader Ruth Davidson recently gave a speech on extending tax powers.
The Liberal Democrats set up a commission chaired by former leader Sir Menzies Campbell which recommended a “Home Rule” option for Scotland.
But the findings come shortly after the Scottish Labour conference, which was marked by deep divisions over a proposal to devolve all income tax to Scotland, with Scottish Westminster MPs mostly opposing it.
Scottish Labour leader Johann Lamont was forced to put the proposal out to consultation and there were suggestions from sources close to UK leader Ed Miliband that he was not happy with the idea.
The poll findings led the SNP to conclude that voters did not accept the promises of pro- Union parties on extending devolution. An SNP spokesman said: “This is a very important finding, because it demonstrates that just a third of people in Scotland believe the No campaign’s case that more powers would follow a No vote.
“And the Westminster agenda is now being driven by Ukup – which is just as hostile to Scottish self-government as it is to Europe.
“This poll reinforces that the sure and certain way for Scotland to gain the powers we need to build a fairer society and stronger economy is with a Yes vote in September 2014.”
The poll of 1,006 voters also revealed that two-thirds of Scots, 67 per cent, believe that the UK and Scottish governments should open negotiations on independence ahead of the referendum on 18 September next year, a move opposed in Whitehall but being pushed by the Scottish Government.
SNP Deputy First Minister Nicola Sturgeon said: “This is an extremely encouraging finding and indicates that the reasonable and constructive approach the Scottish Government are taking in the referendum debate is in tune with the vast majority of people in Scotland.
“By contrast, Westminster’s refusal to enter into pre-referendum discussions so that they can help inform the debate is out of touch with the people.”
Scottish Secretary Michael Moore said the SNP’s concern for more devolved powers after the 2014 referendum was a sign it was losing the argument on independence.
He said: “When those who propose independence are worrying about devolution, it means they are losing the argument. We have seen that is the case on the EU, on Nato, on currency and on pensions in recent weeks.
“This referendum is about independence, just as the Scottish Government pledged. Those who want Scotland to leave the UK family should have the courage of their convictions in making that case – and sticking to it.”
More powers, including a Scottish income tax in 2014, are being devolved to Holyrood through the Scotland Act, passed last year.
Mr Moore also said that the two papers published by the UK government so far – on currency and the legal framework – had seen key independence arguments “hit a wall of hard facts”.
He promised the next 500 days would see “no let-up in the case for independence being tested by the positive evidence for staying in the UK”.
He said: “Scotland is facing a huge decision about its future. But each attempt by the Scottish Government to explain the irreversible change they want has hit a wall of hard facts – the case for independence, based on wishful thinking, is simply not working.”
The poll was dismissed by Better Together, the umbrella group chaired by former Labour chancellor Alistair Darling leading the opposition to independence.
A spokesman said: “All three parties are exploring further options on powers. These will be presented to the people of Scotland over the next few months.”
A Scottish Labour spokesman said: “The only party threatening devolution is the SNP, which wants to break away from our neighbours while still keeping George Osborne in charge of our borrowing and interest rates.”
Salmond: If we’re not in sterling, we won’t take on UK debt share
First Minister Alex Salmond has threatened that an independent Scotland would not take its share of UK debt if it is excluded from a sterling currency zone.
Writing in a newspaper column yesterday, Mr Salmond claimed that the pound was a shared asset and warned that Chancellor George Osborne’s suggestion last week that Scotland would not be allowed into a sterling currency zone was “playing with fire”.
However, opponents have warned that if Mr Salmond takes that position should Scotland’s voters back independence, then the newly independent Scottish state would start life by defaulting on its debts.
In his article, Mr Salmond wrote: “George Osborne is playing with fire with his suggestions that Scotland shouldn’t use the pound as an independent country. That’s because sterling is a jointly shared asset which we are entitled to inherit.
“And if the Westminster government’s position is that we should not be entitled to our own currency and other shared assets, then the only logical extension of that argument is that an independent Scotland will not inherit any share of the UK’s debts.”
The threat was dismissed as dangerous for Scotland by Better Together, the umbrella group leading the campaign to keep Scotland in the UK.
A spokesman said: “The First Minister wants a separate Scotland to start life by defaulting on its debts.
“All sense has left the building.”