UK's Cameron shifts tack as election campaign fails to shift dial

* UK faces close election on May 7

* PM Cameron campaigns on the economy

* Opinion polls remain largely static

* Cameron's party trials new strategy

By Andrew Osborn

LONDON, April 24 (Reuters) - British Prime Minister David Cameron's advisers thought his economic record would have delivered a solid poll lead by now. Instead, as the May 7 election approaches, the polls are largely static and a new strategy is being tested.

The absence of a breakthrough coupled with a stronger than expected performance from Ed Miliband, the leader of the opposition Labour Party, is dampening the mood in Cameron's centre-right Conservative Party.

"The worst thing is when (Conservative) Central Office tries to be helpful," one Conservative candidate told Reuters.

"On the doorstep, when you speak to voters, very little is changing. The campaign has been almost genteel."

The election, which could determine Britain's place in the European Union and Scotland's future in the United Kingdom, is the closest since the 1970s with the two main parties unable to open up a clear lead.

That has prompted both to run heavily scripted campaigns. So far, there have been no gaffes or colourful incidents.

Disrupting voter behaviour this time round is the rise of former fringe parties such as the anti-EU UK Independence Party (UKIP)and the Scottish National Party (SNP).

The SNP is threatening to all but wipe out Labour in Scotland, while UKIP is likely to steal large numbers of Conservative voters in England, making it harder for Cameron to beat Labour in areas where Miliband's party is narrowly behind.

'IT'S THE ECONOMY STUPID'

Cameron's camp had been banking on a simple message to return it to office: That the Conservatives, who have presided over an economic recovery, offer solid financial stewardship compared to the "chaos" of left-wing Labour, which left Britain with significant debts when it left power in 2010.

It looked like an easy sell.

Cameron has helped nurture a recovery that has lifted the economy out of its deepest downturn since World War Two to give Britain one of the fastest growth rates in the developed world.

Lynton Crosby, Cameron's Australian election guru, therefore told the Conservatives to focus on that.

His philosophy, fellow advisers say, is that "you can't fatten a pig on market day," meaning voters need to be bombarded with a message well in advance of polling day for it to "take."

The Conservative problem is that it hasn't yet worked.

Labour has sown doubts in voters' minds, accusing the Conservatives, who have made deep cuts to public spending, of delivering a recovery for the rich at the expense of the poor.