The UK Independence Party claims not to be 'anti-European' - it just does not want to be part of the EU.
Former Tory peer Lord Pearson of Rannoch took over as leader last year
It says the increasing numbers of laws coming from Brussels are threatening Britain's independence.
The party particularly objects to Europe's interference in tax policies and believes that Britain should be ruled by its own elected parliament while enjoying free trade with EU nations
While UKIP takes a firm line on immigration - an end to the "open-door policy" that comes with EU membership - it says it is "non-discriminatory".
UKIP formed in 1993, but in its early days was overshadowed by the well-financed Referendum Party, led by Sir James Goldsmith, which was wound up soon after the 1997 election.
Since then it has made gains at successive European elections, winning its first three seats in 1999 with 7% of the vote.
The party built on that in 2004, winning 12 seats and pushing the Lib Dems into fourth place.
The 2009 poll saw their total grow to 13 seats and the party pushed Labour into third place.
General elections, however, have been a very different story and in 2005 the party failed to make the breakthrough it had been hoping for.
It lost its deposits in at least 451 seats - costing it about £225,500. Even its then leader, former Tory MP Roger Knapman, could only poll 7% of the votes in Totnes, Devon.
The party will be hoping for a big improvement this time around under new leader Lord Pearson of Rannoch.
Succession of leaders
UKIP's website puts its 2005 electoral "slip" down to "internal difficulties" - the party has been dogged by in-fighting over the years.
Founder Alan Sked quit before the 1999 elections after arguing the party should refuse seats in the "gravy train" of the Strasbourg Parliament.
Shortly after that, the national executive lost a no confidence vote and leader Michael Holmes resigned, though he remained an MEP.
Nigel Farage worked hard to end UKIP's image as a single issue party
Mr Knapman took over the role of leader in 2002, but in 2004, a new pretender to the crown - former Labour MP and chat show host Robert Kilroy-Silk - arrived in a flurry of media publicity to shake things up once again.
Before long he was openly jockeying for the leadership, but when Mr Knapman refused to stand aside, Mr Kilroy-Silk went instead.
In 2006, Mr Knapman retired, to be replaced by Nigel Farage, a polished media performer who pledged to make UKIP a "truly representative party", ending its image as a single issue pressure group.
But, despite success at the 2009 European elections and raising UKIP's profile, he surprised his own party conference in September 2009 by standing down as leader of the party - although he continues to lead its group of Euro MPs.
Mr Farage said he would instead run for a seat in the Commons - specifically the seat of Commons Speaker John Bercow, which, by convention, other major parties do not fight. Mr Farage said it was "very important that UKIP gets a voice in Westminster".
Robert Kilroy-Silk left UKIP to found his own party, Veritas, in 2005
Eton-educated Lord Pearson was Mr Farage's favourite choice to replace him but the peer is not afraid to be controversial, inviting controversial Dutch MP Geert Wilders to show an anti-Islam film in the House of Lords - prompting angry scenes outside Parliament.
UKIP itself does not shy from controversy, recently calling for a ban on face-covering veils like the burka being worn in public.
And Mr Farage is not afraid of ruffling feathers in Europe where he continues to make headlines, most recently for telling the President of the European Council Herman van Rompuy he had "the charisma of a damp rag".