One of the world's leading naturalists Sir David Attenborough has cautioned Australia against pursuing further population growth, labelling an unlimited expansion a kind of madness.

Speaking before touring Australia next month, Sir David questioned why the country still found itself actively debating whether it needed to grow its population.

''Why would you want to do that? I don't understand that. The notion that you could continue to expand and increase and grow in an infinite way on a planet which is finite, is a kind of lunacy. You can see how mad that is by the expression that you can't believe that you can grow infinitely in a finite place - unless of course you're an economist,'' he said.

According to the Bureau of Statistics, Australia's population is estimated to grow to between 30.9 million and 42.5 million people by 2056.