ern's: David Cameron's fightback hit by poll slump

Conservatives eight points adrift in new Guardian/ICM poll as prime minister admits, 'I want us to raise our game'

The scale of the challenge facing David Cameron as he began a political fightback has been laid bare by a new Guardian/ICM poll showing Labour has leapt into an eight-point lead.

In the wake of a series of government mishaps since the budget, the poll showed the Conservatives down six points in a month from 39% to 33% while Labour had risen from 36% to 41%, giving the party its best poll lead for five years. The slump overturned what had appeared to be a stable Tory three-point lead ahead of the budget. The Lib Dems remain on 15%.

The Conservative slide is the biggest seen in the monthly Guardian/ICM series since the autumn of 2008, when the onset of the credit crunch briefly produced very volatile political conditions.

The sudden Tory collapse also appeared to be tarnishing Boris Johnson's chances of being elected as London mayor, with a separate YouGov poll showing Johnson with a two-point lead, down from his previous steady six-point advantage over Ken Livingstone.

In an attempt to give the government renewed focus after a torrid month in which ministers stumbled from one unforced error to another, Cameron admitted: we need to "raise our game". He insisted, however, that the government's "driving vision" to eradicate the deficit remained intact.

"In two years, to have a couple of bad months is not surprising," he said.

But the prime minister admitted that the government made an "important mistake" when Francis Maude, the Cabinet Office minister, advised motorists to stock up on petrol ahead of a possible fuel strike. "Sometimes a presentational mistake can be an important mistake," Cameron told the BBC as he admitted to poor communications by ministers.

The former head of the civil service Lord O'Donnell also rounded on ministers on Monday for blaming the civil service for government mistakes. The normally mild mannered O'Donnell told Radio 4's PM programme: "When governments go through difficult patches you are looking for who you can blame. The issue comes up of 'well, let's try and blame the civil service'. It does not usually work and I don't think it will work this time either."

There will be further pressure today from a committee of MPs blaming a lack of strategic thinking for a series of policy mistakes. "Policy decisions are made for short-term reasons, little reflecting the longer-term interests of the nation," MPs on the Commons public administration select committee will say. "Poor strategic thinking militates against clear presentation, which was evident in the aftermath of the budget and in response to the possibility of industrial action by tanker drivers."

Cameron's mood was darkened further by a stinging personal attack on the clique at the top of government delivered by the rightwing Tory backbencher Nadine Dorries. She said: "Unfortunately, I think that not only are Cameron and Osborne two posh boys who don't know the price of milk, but they are two arrogant posh boys who show no remorse, no contrition, and no passion to want to understand the lives of others – and that is their real crime."

Cameron also faced a growing revolt over the coalition's plans for Lords reform on the day a joint committee of peers and MPs proposed a post-legislative referendum on an elected 450-strong second chamber.

Tory MPs were urging Cameron to adopt a "reform plus" package including removal of remaining hereditaries, and reduction of prime ministerial patronage, but no attempt to create an elected chamber. That would be regarded as unacceptable by the deputy prime minister and Liberal Democrat leader, Nick Clegg.

Labour will be pleased its rating has exceeded the 40% mark – often said to be the benchmark for a clear election win. Its 41% score is the party's strongest showing in the Guardian/ICM series since May 2003. At that time, Iain Duncan Smith was trying to turn up the volume as the Tory leader in opposition to Tony Blair.

Ed Miliband personally regards the fallout from the budget, including the decision to cut the top rate of tax as the death knell of Cameron's modernisation project. But he recognises that the dominant mood in the country has been disaffection with all political parties, a mood only made worse by the government's rash of mistakes, including the petrol panic.

The Tories will take solace that on the big question of economic competence, the government remains comfortably ahead. Cameron andthe chancellor, George Osborne, are trusted to run the economy properly by 44% of respondents, with 31% believing Miliband and his shadow chancellor, Ed Balls, would provide more effective financial management.

At the end of last year, Cameron and Osborne led Miliband and Balls by 21 points on economic management, a gap which narrowed to 18 in January and 17 just before the budget, before narrowing by another four points this month.

But Miliband is still unable to convince the electorate of his leadership potential. By wide margins, voters reject the idea that any of the three party leaders "understand people like me", and also the suggestion that any of them are "good in a crisis". On both scores, Miliband's standing is somewhat worse than his already negative scores in December.

The big difference, however, concerns Cameron's perceived competence. At the turn of the year, by 50% to 40% voters trusted him in a crisis. But that 10-point advantage is now a 13-point deficit.

The poll asks about voting intentions for Westminster as opposed to the upcoming council elections, where there has been speculation that fringe parties may do well.

Some recent polls have shown a surge in support for the UK Independence Party (Ukip), suggesting it could even push the Lib Dems into fourth place. But ICM puts it on just 3%, up two points from 1% a month ago.

The UK scores for other smaller parties are: 4% for the Scottish Nationalists, 1% for Plaid Cymru, 2% for the Greens, 1% for the British National Party and 1% for other minority groupings.

ICM Research interviewed a random sample of 1,000 adults aged 18+ by telephone on 16-22 April 2012. Interviews were conducted across the UK 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.

Tom Clark

Patrick Wintour