Britain's anti-EU UK Independence Party launched its election manifesto on Wednesday, appealing to Conservative voters with pledges to raise defence spending and bring forward a vote on Britain's EU membership.

Party leader Nigel Farage unveiled the policy document in front of activists in Thurrock, east of London, ahead of the May 7 vote in which it hopes to win a handful of seats in parliament.

Although only polling at below 15 percent, UKIP could have an important bearing on the make-up of the next government, either as a player in coalition negotiations in the absence of a clear election winner, or by depriving the Conservatives of crucial votes in marginal seats.

Farage vowed to spend "substantially" more than NATO minimum of two percent of GDP on defence in a move that he said would "rattle the dwindling number of Conservative voters who still see (Prime Minister David) Cameron's party as the party of security"

The manifesto spelled out plans for an in-or-out referendum on Britain's membership of the European Union "as soon as possible", a five-year ban on unskilled immigration and a points-based system for more skilled immigrants.

"You will find serious, fully-costed policies that reflect what UKIP is all about: believing in our country," said Farage.

"If you believe that we are big enough to make our own laws, in our own parliament; if you believe we should have the sovereign right to control our own borders; if you believe that we should be fiscally responsible, and stop adding to our national debts and expecting our children and grandchildren to pay the bill, then we are the party for you," he added.

The anti-mass immigration party, which had two MPs at the end of the last parliament, also promised to cut small-business taxes and boost funding for the state's National Health Service.

Cameron, who unveiled the Conservative manifesto on Tuesday, has promised an in-or-out referendum by 2017 if he is re-elected, in a bid to stem the flow of voters from his party's right flank to UKIP -- a trend that threatens to hand the main opposition Labour Party victory in key marginal seats.

But Farage, who is standing to become an MP in southeast England, has said he is also hopeful of taking votes from Labour in its working-class heartlands, where immigration has become a hot topic.