The Prime Minister said he was “taking absolutely nothing for granted” as he hit back at critics who accused him of arrogantly assuming he would win on May 7.
Mr Cameron was grilled after addressing an Age UK summit in central London.
His speech to the pensioners’ group was repeated interrupted with heckling from the audience, with many at the event calling for the PM to increase NHS fund.
Taking questions on his leadership comments, Mr Cameron said: “I am taking absolutely nothing for granted.
“My entire focus is on the next 44 days and the general election, which will decide which team runs this country for the next five years.
“I want that to be me and my team but the alternative is it is Ed Miliband and his team, and that is the focus that I have in the days ahead.
“What I did in my kitchen is I gave a very straight answer to a very straight question and I think that people will understand that - that saying you want to serve a full second term for a full five years is a very reasonable, sensible thing to say.
“So I think we should just focus on the issues at the election about who do you want to run the country for the next five years.”
Shadow chancellor Ed Balls blasted the Prime Minister as “spectacularly self-indulgent, presumptuous and arrogant” for giving the impression of taking victory for granted when the country goes to the polls in May.
Setting out his pitch to pensioners, Mr Cameron said: “I know that some of you will have seen the election carnival roll around many times before –but this election really matters.
“And the choice couldn’t be more simple.
“You can stick with the strong, competent team that is turning our country around – or you can choose the lot that got us into the mess in the first place.”