By Andrew Osborn
LONDON (Reuters) - Signs of a fledgling economic recovery in Britain have boosted voter trust in Prime Minister David Cameron's financial stewardship, strengthening his prospects ahead of an election in 2015, a poll showed on Tuesday.
The Guardian/ICM survey said that 40 percent of voters trusted Cameron and his Conservatives on the economy, up sharply from 28 percent in June, and comfortably ahead of the opposition Labour party, whose economic credentials won approval from just 24 percent of those asked.
The health of the economy and political parties' perceived ability to nurse it back to sustained growth after three rocky years is likely to be the single most important factor in deciding who wins the 2015 election.
The economy has shown unexpected signs of improvement in recent months with the Bank of England forecasting it will grow by 0.6 percent during the current quarter, the same as between April and June, and that growth will reach an annual rate of 2.6 percent in two years' time.
Labour remains a few points ahead of the Conservatives in the opinion polls but has seen its lead shrink after better economic data, even though many economists believe it is too soon to talk of a sustained recovery and are concerned about a possible housing price bubble.
Tuesday's poll put Labour's overall support at 35 percent, a mere three percentage points higher than the Conservatives.
Cameron, who governs in coalition with the center-left Liberal Democrats, has put the economy at the heart of his re-election strategy, hoping a strong recovery will materialize and create a feel-good factor that will allow his party to govern alone next time.
According to Peter Kellner, of pollster YouGov, an improving economy poses a problem for Labour leader Ed Miliband.
"Now that Britain's economy has started to recover, he is likely to face a prime minister who can copy one of the slogans that Barack Obama used last year to secure re-election," he wrote.
"The president likened America's economy to a car that his predecessors had driven into a ditch. 'I don't want to give them the keys back,' he said. 'They can't drive'."
Labour, which governed Britain from 1997 to 2010, was in power when the global financial crisis hit and says it was managing the economy well but was knocked off course by events.
The Conservatives say Labour left Britain with its biggest budget deficit since World War Two and cannot be trusted to manage it again anytime soon.
Alastair Campbell, who was former Prime Minister Tony Blair's chief communications adviser, said Labour had allowed the Conservatives to unfairly cast them as the creators of the economic turmoil that followed the financial crisis.
"Britain had 10 good years of growth and prosperity under Labour which is one of the many reasons we won three elections and stopped David Cameron winning a majority," he wrote on his blog.
ICM Research interviewed 1,001 adults by phone on August 9-11.
(Editing by Robin Pomeroy)