Labour support falls to 31%, Conservatives rise one point to 33%, Lib Dems are up one on 13% and Ukip rises four to 15%

Labour's support is draining away, according to a Guardian/ICM poll which records the first Conservative lead in over two years and gives Ed Miliband's party its smallest share of the vote for four years.

The Tories are on 33% in the monthly state of the parties poll, up a single point and two points ahead of Labour, which has sunk by six points since April. The poll will add to Labour nerves a week and a half before European and local elections, and less than a year before the general election.

Flush with publicity of all kinds before the European ballot, Nigel Farage's Ukip climbs four points to 15%. The Liberal Democrats edge up one to 13%. The ICM finding is surprising because although polling averages have pointed towards a narrowing gap between the two main parties, internet polls for the Sunday papers pointed to continuing Labour leads of between four and seven points.

However, a second telephone poll published on Monday, sponsored by the Tory peer Lord Ashcroft, also points to a two-point Conservative lead. That poll has the Tories on 34% against Labour's 32%.

Haunted by memories of the Thatcher/Major years, when healthy opposition leads during mid-term repeatedly disappeared in the runup to polling day, Labour has long feared that Miliband's edge may not be big enough to take the party safely into power next May.

As a nervous Labour party seeks an explanation for its dwindling ratings, it may take some comfort from the fact that the Tories have barely advanced. However, with Europe, immigration and an improving economy in the spotlight, the party will now be wondering whether it faces an even stiffer task in persuading an uncertain country to entrust it again with the levers of power.

Labour's low ebb in the Guardian/ICM poll goes hand in hand with negative views of its leader. Despite a month in which Miliband has put regulation of rental agreements on the agenda, and made the running against the government over AstraZeneca, 51% of voters believe he is doing a bad job, twice as many as the 26% who think he is doing well, giving him a net negative rating of -25.

This is the worst score for him that ICM has recorded on this occasional question, although it is only marginally worse than the net -22 he notched up when it was last asked, a year ago.

What has changed since then is where this leaves Miliband in relation to other political leaders. Nick Clegg remains comparably unpopular, with 51% also believing him to be doing badly and just 30% rating him as doing a good job.

But whereas David Cameron and George Osborne were also in negative territory last spring, after a year in which the economic recovery has picked up pace their standing is now much improved.

Some 44% of voters believe the prime minister is doing a good job, against 42% who say the reverse. That gives him a net rating of +2, which compares with -15 last May.

The bounceback in Osborne's stock is more dramatic. After the "omnishambles" budget of 2012, his net score was -25, and in April 2013, when the question was last asked of the chancellor, it was -14.

But in the latest poll, 41% of respondents tell ICM that he is doing a good job, against just 36% who regard him as doing badly, which gives him a net +5.

ICM's monthly phone survey is best interpreted in the light of wider trends. Labour opened up a clear lead during the first half of 2012, after Andrew Lansley's NHS reforms turned controversial and more particularly after that unpopular budget.

Ukip is now within three points of the 18% it notched up a year ago, in its best ever score with ICM. Curiously, however, the party's resurgence comes alongside flagging enthusiasm for Farage.

In May last year, his job approval rating was +17. Today, 39% say he is doing a bad job as against 31% who see him as doing well, giving him a negative net rating of -8.

Among Lib Dem voters his score is -20, among Labour supporters -28, and even among Conservatives he notches up -11. By contrast, among his own tribe, his popularity is overwhelming: 93% of Ukip backers believe Farage is doing well, suggesting support for the man is translating into support for the party.

Clegg just scores in positive territory among current Conservatives, a contrast with 2010 Lib Dem voters, who now believe that the man they supported last time around is doing a bad job, by 44% to 40%.

Miliband can draw some comfort from the narrow majority of current Labour voters, 52%, who believe that he is doing well, although – after Labour's "incredible shrinking man" broadcast assaulting Clegg – he will be disappointed that 54% of 2010 Lib Dems rate him as doing badly.

ICM also asked more specifically about voting intentions for next week's European elections. With only 37% of electors suggesting they are certain to cast their ballot, such projections inescapably depend on fewer respondents than those for Westminster.

Even so, the news is again encouraging for the Conservatives, and worrying for Labour.

The Tories are up two on April, which puts them on 27%, and in a virtual dead heat with Ukip, which has bounced up four in the European stakes to stand at 26%. Labour sinks by 12 points on April, to 24%, with appreciable proportions of the party's 2010 votes moving to Ukip and the Greens.

Together with Lib Dem defectors –Clegg's party languishes on 7% – this helps push the Greens up four and into a clear fourth place, on 10%. The Scottish and Welsh nationalists are on 2% each, and assorted independents and others notch up 3%.

Voters across the United Kingdom will elect 73 members of the European parliament next week. There are also local council elections for 4,200 seats in 161 councils and direct elections for mayors in four London boroughs. Labour is looking to reach at least 35% in the council elections. The polls are the last major test of public opinion before the general election, which is set for 7 May 2015.

• ICM Research interviewed a random sample of 1,000 adults aged 18+ by telephone on 9-11 May 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.