Referring to Mr Little as "angry Andrew, Mr Key told reporters the public would not take Mr Little seriously while he was "just bashing out slogans" and not coming up with policy.
He said the Government was required to set a surplus target or deficit target, a growth target, and an unemployment target which were calculated by the Treasury - on the basis of Government policies.
"They are our best estimate," Mr Key said. "If you go and have a look at three years ago at what Treasury thought we'd be spending today, we are actually spending $4 billion less. Is that deception? No, it's actually good economic management."
He said no one could actually know so an estimate was put on it.
"We've come from a $18 billion deficit five or six years ago to pretty much a surplus. I think most New Zealanders would say that's the right step."
In later year's Budget, Finance Minister Bill English forecast a $372 million surplus for the current year which ends in June.
It was downgraded in December's half-yearly update to a deficit of $570 million but he still hoped a surplus could be achieved. Last week he officially gave up hope, confirming that the Budget on May 21 would forecast the year ending in the red with a slightly bigger than the one forecast in December.
It was the second day in a row that Mr Key has referred to Mr Little as "angry Andrew" or "angry Andy," - a name that backbenchers gave to him in his first term in Parliament during heated parliamentary debates.
Mr Little said it was good for people to have "he was "angry about this Government's failure in seven years to actually make a difference to New Zealand and our economic prospects."
"He will throw around the labels as much as he likes. People are getting to know me but they want someone who is actually passionate about New Zealand, who is not in the Prime Minister's job as a vanity project and that's the difference between him and me."
National was a bystander to the economy for the past seven years.
It cheered on dairy prices and oil prices but now they had fallen, the Government did not know what to do.
"They don't have any ideas. We've got a guy in the Prime Minister's office who thinks it's okay to be kind of jokey blokey and go round and pull people's hair as part of his persona."