Ukip vows to show it can upset the Conservatives – as well as Europe

Conference arrives with party on verge of becoming serious thorn in PM's side, says Farage

The UK Independence Party will begin its annual conference today with a bold attempt to demonstrate that it is more than a single-issue party dedicated to getting Britain out of the EU.

The leader of Britain's fourth party, Nigel Farage, believes that it could be on the verge of attracting big-money donors disillusioned with David Cameron, which could enable it to become the largest British party in the European Parliament.

In the 2009 European elections, which use a system of proportional representation, Ukip collected 2.5 million votes, pushing Labour into third place and giving them 13 MEPs – one of whom, Nikki Sinclaire, was expelled the following year after making an unsuccessful bid to become party leader.

Today, the party's energy spokesman, Roger Helmer, will call for the UK to abandon wind farms and other types of renewable energy to fall back on the traditional methods of generating electricity – gas, coal and nuclear power. Despite the volume of scientific research about the causes of global warming, Mr Helmer will tell his audience that the "theory" that climate change is caused by human activity is "unproven and implausible", and that renewable energy is destroying jobs in traditional industries. The message is likely to appeal to Tories who never liked Mr Cameron's promise to head the greenest government ever.

While the Ukip assembly in Birmingham will be buoyed by recent opinion polls that have put it level or ahead of the Liberal Democrats, the party's leaders are anticipating a hostile reaction to the possible image makeover, which could see its official name, the UK Independence Party, abandoned in favour of the shorter acronym Ukip. The Party chairman, Peter Crowther, has put out a message to supporters which said: "We are reviewing the brand. We have not decided how it will develop, though Nigel rightly points out some of the key considerations: the strength of the short name 'Ukip', the fact that the pound sign can be off-putting to some people, the value of our colours." He added: "If you'd like to remonstrate with me about it – come to Conference."

Lord Stevens of Ludgate, who was expelled from the Conservatives in 2004 for encouraging people to vote Ukip, and who has now joined the fourth party, claimed: "The problem the Conservatives have is that Ukip is now becoming a serious political party." That view is privately shared by many Tories.

Defections to Ukip are thought to have cost the Conservatives 20 seats in the 2010 election, with the possibility that they could inflict even worse damage to Tory support next time. One Tory MEP, Danial Hannan, is openly calling for an election pact with Ukip.

The party has selected a local businesswoman, Margot Parker, as their candidate in the impending by-election in Corby, where they are hoping to take second place, behind Labour.