* Group backs Cameron's call for new British role in Europe
* More than 500 business figures support campaign
* They want looser ties; debate widens before 2015 vote
* PM's pledge to claw back powers angered EU leaders
By Peter Griffiths
LONDON, April 22 (Reuters) - Prime Minister David Cameronwon the support of 500 business leaders on Monday in hiscampaign to renegotiate Britain's ties with the European Union,a political gamble that has infuriated some of the bloc'sbiggest members.
Business for Britain, a new lobby group, said it backedCameron's plan to repatriate powers from Brussels and hold areferendum on Britain's EU membership, provided his ConservativeParty wins the next election.
France and Germany have attacked Cameron's stance, sayingthey will block any attempts by London to "cherry pick" EUpolicy. The United States has said it wants Britain to remaininside the EU.
Other business groups say the referendum pledge riskscreating uncertainty that will deter investment, isolate Britainand stifle the stagnant British economy.
However, the new lobby group said cutting regulation,scrapping a planned financial transaction tax and allowinglooser ties between its 27 members would benefit Britain andboost growth across a continent shaken by a debt crisis.
"Many would have you believe that business doesn't wantpoliticians to try and renegotiate a better deal from Europe,"said Alan Halsall, the group's co-chair and chairman of SilverCross, a company that makes baby products. "Jobs and economicgrowth depend on a more flexible, looser relationship with theEU."
BATTLE LINES
Since Cameron came to power in 2010, the long and bitterdebate over Britain's place in Europe has resurfaced. Groups onboth sides of the argument have begun drawing up battle linesbefore an election due in 2015.
Cameron, who wants to stay inside the EU, trails the LabourParty in the polls and is threatened by the UK IndependenceParty, an increasingly popular anti-EU group wooing disgruntledConservatives.
The British leader is under pressure to appease Conservativelawmakers who want him to take a tougher line with Brussels,seen by euro sceptics as a wasteful, interfering bureaucracyeroding British sovereignty.
On the other side of the debate, the pro-EU camp says closeties with the EU, Britain's biggest trading partner, are vitalat a time of intense global competition.
Among the 500 signatories of a letter sent by Business forBritain to newspapers to launch its campaign were Simon Wolfson,chief executive of retailer Next Plc ; Stuart Rose,chairman of online retailer Ocado Group Plc, andRichard Burrows, chairman of British American Tobacco Plc.
Business for Britain describes itself as an independent,cross-party group funded by donations from business supporters.
A poll last week for the British Chambers of Commerce, alobby group that represents more than 100,000 companies,suggested some support for the group's position.
Nearly two-thirds of those polled (64 percent) saidBritain's economic prospects would improve if it stayed insidethe EU on renegotiated terms.
Sixty percent said withdrawal would be bad for business andthe economy; 18 percent said it would have a positive impact.