Nigel Farage set out plans for an early referendum on withdrawal from the EU, a radical reduction in immigration, increased spending on defence and an £18 billion tax giveaway as he launched the Ukip manifesto under the slogan Believe In Britain.

Declaring "we want our country back" Mr Farage said that Ukip was the only party in the May 7 General Election to argue that the UK should be a free self-governing nation, able to make its own laws and negotiate its own trade deals, and trading with the European Union as "good neighbours".

After dismissing the Ukip manifesto for the 2010 election as "drivel", Mr Farage said that the spending and saving commitments in this year's much slimmer document was fully costed and independently verified by the Centre for Economics and Business Research thinktank.

Launched in the Ukip target seat of Thurrock in Essex, the manifesto has at its heart an early referendum on Britain's EU membership, which Mr Farage believes will pave the way for withdrawal, allowing the UK to impose tighter immigration controls and thereby relieve pressure on public services.

Other flagship policies included:

- An £18 billion "low tax revolution" which would see the threshold for paying income tax raised to £13,000, the higher-rate 40p threshold lifted to £55,000 and a new 30p rate on earnings between £45,000 and £55,000.

- Savings totalling £32 billion by the end of the Parliament in 2020, including a "radical" cut in overseas aid; the ending of contributions to the EU; the scrapping of "vanity projects" like the HS2 rail link between London and the North; and reform of the system for distributing of state cash, to cut funding for Scotland and give a "fairer deal" for England and Wales.

- A commitment to meet and then "substantially" exceed Nato's target of 2% of national GDP to be spent on defence, and to end tax payments for armed forces on active service.

- Increased spending of up to £3 billion a year on the NHS.

With Ukip in no position to secure an overall majority in the May 7 General Election, the manifesto will widely be seen as setting out a negotiating position for coalition discussions with larger parties - particularly the Conservatives - in the event of a hung Parliament.

Mr Farage has made clear he will put pressure on David Cameron to bring forward the in/out EU referendum he has promised for 2017, and he dismissed the Prime Minister's plan to seek reform of the UK's membership ahead of the poll, insisting that there was "no renegotiation of any value that is to be had in Brussels".

The Ukip leader said: "We are the only party with the self-confidence and belief in this nation 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 international trade deals.

"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 that we can set this country free from political union.

"There is no third way. There is no renegotiation of any value that is to be had in Brussels. Our position is perfectly clear - We want our country back."

Answering questions following the manifesto launch, Mr Farage denied having started formal talks with Conservatives over a possible post-election deal.

"Can I make it absolutely clear, I have not put any feelers out to anybody over the course of the last week or month and nor will I be between now and May 7," said Mr Farage.

"I have no intention of speaking to anybody other than the British public in as large a number as I possibly can."

He added: "What do I think is the most important part of this manifesto, without which we wouldn't even contemplate doing a deal of some kind - which doesn't mean a coalition, incidentally? It is without doubt that the people of this country have a full, free and fair referendum on our membership of the European Union, not a pro-EU government-led stitch-up."

Mr Farage said Ukip was attracting former supporters of the Conservatives, Labour and Liberal Democrats, but said the "absolute key" to its performance on May 7 was people who did not vote in 2010 and in some cases have not voted for many years - or even their entire lives - and see Ukip as "a positive party that offers them hope".

Asked whether he had been involved in informal discussions about potential post-election arrangements with Conservatives, Mr Farage said: "If I meet people in a social environment, I'm a gregarious cove and I generally speak to them.

"We have discussions with people who are in all of the other political parties, yes, of course that goes on. What was being said in one of the newspapers this morning was that formally we have been having conversations, and that hasn't happened and it won't be happening."

Mr Farage said he stood by his call to keep HIV-positive "health tourists" out of the UK.

The manifesto said Ukip would keep foreign criminals out of the UK and deny migrants benefits until they had been in the country paying taxes for five years.

Migrants would be admitted to the country on an Australian-style points system which would allow up to about 50,000 people with in-demand skills to enter the UK each year.

But Mr Farage insisted he was not setting a "cap" on net migration numbers, saying: "The only way you can effectively set a net migration target is to be like the former Communist countries, where you don't allow anyone to leave. Because if you don't do that, it is impossible to have any net migration figure.

"What we have said is up to 50,000 skilled workers, who will pass all the right tests using the Australian-style points system, will be welcome to come into Britain every year.

"We won't set an arbitrary cap, we will aim to bring immigration to this country back to normality, back to that figure that it ran at up to 1998, when ... we had between 20,000 and 50,000, perhaps an average of 30,000, people a year net coming to Britain."

The launch, at the Thurrock Hotel, was a boisterous meeting of keen Ukip supporters with frequent ripples of applause and cheers.

But the mood soured during the question-and-answer session from journalists.

Mr Farage was asked why the manifesto featured black faces on only one page, prompting shouting and jeers.

A group of black and Asian activists were cheered when they stood up in the middle of the press conference.

The Ukip leader did not appear to answer the question about images in the manifesto, which is dominated by pictures of Ukip spokesmen and women.

Journalists were heckled again when Mr Farage was asked to stand by his remarks about stopping foreigners with HIV entering Britain for treatment on the NHS.