By Peter Griffiths LONDON (Reuters) - A rich British businessman said on Monday he would "do whatever it takes" to help the UK Independence Party fight next year's European Union polls, where gains for the anti-EU group could hurt Prime Minister David Cameron's chances of winning a second term. UKIP, a right-wing group that wants to leave the EU and impose tighter immigration controls, is leaching support from Cameron's Conservatives and poses one of the biggest obstacles to his re-election at a national poll in May 2015. A strong UKIP performance in the European parliament elections in May could widen historic Conservative divisions over Europe that Cameron had hoped to heal in January with a promise of a referendum on membership of the 28-nation bloc. Paul Sykes, a Eurosceptic former Conservative supporter, said he wanted to force the main parties to "abandon their slavish support for the EU" and bring forward the referendum, which Cameron says will take place by the end of 2017.