Labour’s lead is down to three points according to the latest Guardian/ICM poll as data shows that the combined score for the three main parties is at an all-time low.

Ed Miliband’s party is not trusted to run the recovering economy, but the modest Tory rise is accompanied by rising concern about the NHS, seen by voters as the No 1 issue.

The Conservatives gain two points to reach 30%, while Labour remains unchanged at 33%. The Liberal Democrats fall back three points to just 11%.

“The parties we used to relegate to the margins with the term ‘others’ are now moving centre stage,” said Martin Boon of ICM. “The combined forces of all those outside the old LibLabCon triopoly has never been stronger during three decades of Guardian/ICM polling.”

Ukip is also down three points at 11%, while the big winners of the latest monthly telephone survey are the Greens, up four points on December to 9%, their highest level for over 20 years according to ICM data. Other smaller parties, most importantly the Scottish National party, have also advanced this month – the SNP’s combined score inches up one to 7%.

With the media dominated by reports of the winter pressures facing the NHS, the health service has cemented its place among the public as the most important policy topic for the election. When respondents were pushed on which single issue would be most important to their vote last October, the NHS was already top. But with growing queues at A&E, it is now more important than ever. Of those polled, 31% name the NHS as their top priority, a rise of seven points since autumn.

The salience of most other issues falls – with second-place immigration dropping back one to 19%, and “jobs, prices and wages” sinking three to 14%. The declining political significance of the economy appears to be the flipside of easing financial anxieties.

Right through the credit crunch, ICM ran a tracker question about people’s confidence in “the economy, your finances and ability to keep up with the cost of living”, and frequently totted up large net negative scores. But by September 2013, the economic optimists and pessimists were evenly matched, respectively numbering 50% and 49%. Today, the mood is much more upbeat – with 61% of Britons saying that they are confident, and just 38% saying that they are not.

This recovering economic mood is sapping strength from Labour: only 15% now say they would trust Ed Balls and Ed Miliband as the team best able to manage the economy properly. By contrast a far higher proportion, 37%, put their faith in David Cameron and George Osborne, giving the Tories a record 22-point advantage on the economic question, which they hope will be decisive in May. But the electorate is not in a mood for gratitude: another 44% of respondents say that they would trust neither team.

And as economic anxieties ease, worries about the health service intensify. Only 11% of voters believe it is working well, against 22% who judge it is feeling the squeeze but coping. That compares with 28% who believe it to be “struggling and not delivering services it should”, and an even more worried 36% who believe it isn’t coping at all, and “in danger of ceasing to exist in the form that Britain has known it”.

While health continues to be a Conservative weakness, the Tories can take some comfort from a question regarding the blame game for rising A&E waits. A substantial minority, 38%, blame “reforms and financial choices” made by the coalition, but a slender majority – 52% – regard the root problem as being “budgetary pressures and mismanagement which would be much the same under any government”.

With many pundits now predicting another hung parliament after May, respondents were also asked about what they would want to happen if there is no clear winner. Go-it-alone minority governments emerge as particularly unpopular, with only 8% favouring the Conservatives trying to rule without a majority, and an even smaller sliver of 3% of electors favouring a minority Labour administration.

Among various multiparty ruling configurations, the most popular option – preferred by 19% – was a Labour-led administration including both the SNP and the Greens. The second most popular option would be a Conservative-Ukip coalition – the choice of 15% – while a Labour-Lib Dem coalition and a second Conservative–Lib Dem arrangement were each preferred by 13%. A “grand coalition” of Labour and the Conservatives is preferred by 9%.

“England may not love coalitions”, said Boon, “but it is certainly learning to live with the idea of multiparty government. Voters’ views on what should happen in a hung parliament – with a large majority preferring some form of multiparty rule – bear out the overall message of this month’s poll. The old political tribes are losing their grip.”

ICM interviewed a random sample of 1,002 adults aged 18+ by telephone on 16–19 January 2015. 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.