A Ukip government would give Britain a £18bn ($26bn) "tax giveaway" in a bid to stimulate "real dynamic growth" in the UK economy, Nigel Farage has promised.

The Ukip leader and Eurosceptic firebrand made the pledge as he launched his party's general election manifesto in Thurrock, Essex.

Ukip plan to move workers who earn up to £13,000 a year out of income tax, raise the threshold on the 40p tax rate to £50,000 a year and introduce an additional 30p band for people earning between £45,000 and £50,000.

Farage also stressed that his party wants a referendum on the UK's membership of the European Union (EU) "as soon as possible" and claimed Ukip are the only party who believe in Britain.

"We are the only party with the self-confidence and belief in this nation to say that we actually believe that not only could we, but that we should govern our own country, make our own laws and negotiate our own trade deals," he said.

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"We are the only party standing in this general election, saying we want a trade deal with Europe, we want to be good neighbours with our European friends, but we desperately seek a referendum so we can set this country free from political union."

The party leader made the announcement alongside Ukip deputy chairman, Suzanne Evans, who spelled out the party's further proposals.

The policies include a plan to abolish inheritance tax altogether, a £12bn boost to the NHS and a five-year ban on unskilled migrants to the UK.

In addition, the party proposed to commit to speak 2% of the UK's GDP on defence spending and build a 500 bed military hospital for veterans and injured or ill members of the armed forces.

Elsewhere, the policy document sets out Ukip's annual net migration target of 50,000 highly skilled workers.

Evans stressed that the manifesto was independently verified by the Centre for Economic and Business Research and she described the document as "serious".

Ukip won the European Parliamentary elections in the UK last year and saw two Tory MPs, Mark Reckless and Douglas, defect to their party.

But the purple outfit has seen a slip in the polls since last year and are now on 13% in the latest survey from YouGov, with Labour two points ahead of the Conservatives (35% vs 33%).

Farage and Ukip will hope the manifesto will boost their support with just 23 days to go before polling day.