More than half of respondents say they would vote to take UK out of EU if a referendum took place tomorrow

The public mood of Euroscepticism is hardening, according to an exclusive Guardian/ICM poll that finds 51% of respondents would vote to take Britain out of the EU, against just 40% who say they would vote to stay in.

The news comes as the prime minister prepares to give a widely anticipated speech on Britain's relationship with the EU in the new year.

The last time ICM asked the same question, in autumn 2011, opinion was already leaning in the anti-European direction, by 49% against 40%, but a slight hardening of opinion since that time means that anti-EU feeling is now just in the majority.

This marks a turnaround from similar polls conducted in the earliest years of this century. When ICM asked a slightly differently worded question in May 2001, the public indicated that it wanted Britain to remain a member of Europe by 68% to 19%.

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Even worse news for the pro-Europeans emerges when respondents were asked about how definite they were in their view. Fully 36% say they would definitely vote to pull Britain out, against just 22% who definitely want to stay in. That compares with 18% who say they would probably want to stay in, and 15% who indicate that they would probably want to get out.

The deteriorating standing of the European Union emerges at the end of a year in which it has won the Nobel peace prize for its success in bringing peace to a continent, but also – and perhaps more significantly – a year which has been marked by the crisis of the single currency moving from an acute to a chronic phase.

The anti-European mood seizing large parts of the electorate was reaffirmed by other questions in the same survey. When voters were asked to provide a "school report grade" for the work of various institutions, the EU was awarded a D+, somewhat worse than the C- average mark awarded to both David Cameron and Ed Miliband. The poll also affirmed that support for the anti-European party Ukip was running at 7% for a second month in a row, a record high in the long-running Guardian/ICM series.

There is a recognisable split on partisan lines, but it is not quite as marked as the very different language about Europe used by the three party leaders might suggest.

Fifty-seven percent of Tories want to pull Britain out, compared with 44% of Labour supporters and 34% of Lib Dems. But Cameron may be interested to learn than only 41% of his party's supporters are definitely committed to pulling Britain out, leaving a majority of Conservatives who retain a more equivocal or pro-European position.

The hardcore "definitely vote to leave" vote is stronger among men, 40% of whom are in this camp, than among women, among whom only 32% take this view. There is a sharp age gradient in Euroscepticism, too; 49% of pensioners aged 65+ are in this hardline camp, compared with just 16% of the youngest voters, aged 18 to 24.

There is a strong anti-European contingent across the regions and social classes, although some signs that hostility to Brussels is more marked in England and less marked among professionals.

Only 32% of voters in the top AB social definitely want to quit Europe, compared with 45% of the skilled manual workers group, classified as C2. Whereas as in England 38% are in this hardline camp, in Scotland and Wales the respective figures are just 27% and 26%.

• ICM Research interviewed a random sample of 1002 adults aged 18+ by telephone on 19-23rd December 2012. 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.