The head of the Reserve Bank of Australia has cast doubts over the figures used to underpin the Abbott government's rosy budget forecasts, warning projections for Australia's future economic growth may be too high.

It is the first time RBA governor Glenn Stevens has weighed into the debate about Australia's "trend' rate of growth", warning: "I suspect this will turn out to be an important discussion."

It means Commonwealth and state governments may have to adjust their expectations of future revenue growth downwards, and the Abbott government's hopes for a budget surplus - which it expects to deliver soon after 2017/18 - could take much longer to realise than expected.

Mr Stevens has also signalled that he has set the bar higher for further interest rate cuts, saying he is wary of encouraging behaviour in the financial sector that could become "dangerous" and spill over into the "real economy".