Election 2015: PM anger at 'party of the rich' claim
David Cameron says accusations the Conservatives are "the party of the rich" make him "more angry than almost anything else".
The prime minister also told the BBC some people did not pay tax in Britain "who damn well should".
If the Conservatives fall short of an overall majority at the general election, he will feel he has "not succeeded", he said.
The prime minister said his party "came close" last time.
In an interview with BBC Newsnight presenter Evan Davis, he was asked about the 2010 election, when the Conservatives missed out on a majority and formed a coalition government with the Liberal Democrats.
Mr Cameron said voters had been "very worried" about the state of the economy and some "weren't fully sure we had all the ideas and plans".
He added: "This time, I believe they can put their trust in me".
'Pledge after pledge'
Asked whether he would see it as a failure if the Conservatives do not get a majority, he said: "We are only 23 seats short and if I fall short of those 23 seats I will feel I have not succeeded in what I want to achieve."
Mr Cameron said he did not "overpromise" in the 2010 manifesto, saying "pledge after pledge has been fulfilled", but acknowledged the Conservatives had not "achieved everything I wanted to".
Neither the Conservatives nor Labour have committed to spending 2% of GDP on defence, while UKIP, which launched its manifesto on Wednesday, says it would meet the Nato target.
Mr Cameron said a "full defence review and spending review" would take place under a Conservative government, adding: "That's the right time to make the final decision."
He said defending the country was "not just about the defence budget" but also about counter terror, intelligence and overseas aid.
In the first of the series of leaders' interviews with Evan Davis, Lib Dem leader Nick Clegg said he would reject another coalition with the Conservatives if they insist on their proposed £12bn welfare cuts.
The Tories have said details of this will be set out after the election, and Mr Cameron said: "What we're proposing is totally affordable and doable."
Asked about the perception that the Conservatives are the "party of the rich", he added: "This makes me more angry than almost anything else."
He said it "infuriated" him because of the government's record, including taking three million of the lowest paid out of tax.
The PM also said the government had "gone after" businesses who don't pay their fair share of taxes.