Mr Key said the Reserve Bank's projections for stalled growth from 2013 should be taken with "a grain of salt''.
"There are a range of views there. The Treasury's views of growth have been a little stronger than the Reserve Bank _ the Reserve Bank's been a little bit conservative on that front,'' he said.
"As a general rule, you want to take those things with a grain of salt. There's a lot of different factors. If we start seeing global growth picking up, then that has a big impact for New Zealand.''
Mr Key said stimulus from the Christchurch rebuild would continue past 2013.
"If the Reserve Bank really believed that there would be no growth beyond 2013 to speak of, then the Reserve Bank would cut interest rates because we still have interest rates at one of the higher levels around the world.''
Mr Key also defended the Government's track record on youth unemployment.
Statistics New Zealand figures show there are 85,000 people aged 15 to 24 who are not in any education, training or employment- up 25 per cent under since Mr Key took power.
Mr Key said recessions were the hardest on lower income, lower skilled and young people.
But he said only 4 per cent of 15 to 19-year-olds did not have a job, with the rest in education or employment. The "great many'' of 20- to 24-year-olds were also in some form of work.