More than six out of 10 people in England and Wales believe the government should bar an independent Scotland from using the pound, according to a Guardian/ICM poll.

The currency question has been a key referendum battleground with Westminster party leaders repeatedly making it clear that Scotland would not be allowed to use the pound; the independence campaigners claim they are bluffing and would eventually allow a union in the case of a yes vote.

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Monday's poll finds that 63% of voters in England and Wales believe that the UK should "refuse to negotiate" over a common currency area if Scotland becomes independent, more than twice as many as the 27% who would favour such talks beginning. This makes for a total contrast with Scotland, where 62% believe that a currency union should be negotiated.

While all eyes are Scotland, the UK as a whole is now only eight months from a general election, which ICM's long-running series suggests is shaping up to be another extremely competitive race. After an unusually strong showing by Labour last month, Ed Miliband's party now slips back three percentage points to 35%.

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The Conservatives bump up two to 33%, possibly helped by Ukip slipping back one to 9%. The Liberal Democrats are also down, by two points, which leaves them on 10%, equalling their worst-ever performance over the last two decades.

Beyond the currency, the poll contains other signs of English unease about the prospect of the union dissolving. Some 50% of English and Welsh voters believe that "England and Wales should also have been given a say", as against just 45% who do not. Fifty-six percent of the English and Welsh say they would be "saddened" by divorce from Scotland, which compares to a mere 40% of Scots who would feel the same way about separating from the rest of the UK.

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But relatively few voters south of the border, just 31%, would be "fearful" for their own country's future after Scottish independence, considerably less than the 40% who would anticipate feeling fearful in Scotland itself.

The small sample from Wales is more nervous again, with 48% expressing anxiety about their own country's future after a Scottish yes.

After the referendum polls began to tighten, politicians from across the political spectrum have rushed forward with various plans for enhanced devolution, in some cases focused on Scotland, in some cases applying more widely. In Scotland, more devolution appears to be the settled will – 81% of Scots would be in favour, with just 16% against. In Wales, too, a souped-up assembly would be popular – with 56% in favour, and only 33% against. In England, however, there is less hunger for constitutional reform.

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Asked about new regional assemblies or a new English parliament, only 45% believe that such things would "benefit the area in which you live", closely matched by the 42% who disagree. And there is no more support for such devolution in the English Midlands, where 43% are in favour, or the English north (44%), where London might seem especially remote, than there is in the English south, where support stands at 47%.

The small print on the voting intention figures suggests that the trenches of the general election 2015 are already dug very deep. There is almost no direct movement between the main Labour and Tory blocs, with just 2% of David Cameron's 2010 voters saying they will turn out for Miliband next time, and only 1% of those who voted for Gordon Brown making the opposite journey. Instead, 88% of 2010 Labour voters are staying loyal, as are 81% of 2010 Tories.

The relative standing of the two depends much more on Labour's success in attracting disaffected Liberal Democrats from 2010 – 36% of whom now plump for Labour, against a mere 33% who plan to stay put – and the Conservatives' ability to stem leakage to Ukip, which this month is attracting 9% of 2010 Tories.

Other non-traditional parties are also making inroads, with the collective share of "others" this month climbing four to 13%, swollen by a particular surge of support for the Greens – who have just held their conference – which takes them to 7%.

On a uniform nationwide swing, the Electoral Calculus website suggests that Labour's slim lead with these figures could cash-in as a small majority of around 20 seats. But Martin Boon, director of research at ICM, cautions that the opposition should not assume that this slim lead is secure. "At this stage of the last political cycle, David Cameron stood some 17 points clear of Gordon Brown, and looked set to barnstorm No 10. He ended up in a hung parliament situation, and with a mere two-point lead Ed Miliband looks considerably less secure than that."

In the event of a Scottish yes, the loss of 41 current Labour seats from the Commons would redouble Miliband's difficulties, but there would be even more immediate problems for Cameron, as the prime minister after "losing" a large part of the realm.

ICM Research interviewed a random sample of 1,002 adults aged 18-plus by telephone on 12-14 September 2014. Interviews were conducted across the country and the results have been weighted to the profile of all adults. ICM is a member of the British Polling Council and abides by its rules.