Dr Philip Hughes of the Christian Research Association said the numbers of people participating in nature religions - mostly witchcraft and paganism - rose by 140 per cent between 1996 and 2001. Agnostics were on the rise too, he said.

For many, nature religions were seen as environmentally friendly.

But Dr Hughes said their numbers remained small, with fewer than 25,000 adherents in Australia.

"They are never going to be really numerous as it is largely a protest movement."

Leading witch Caroline Tully says witchcraft is a religion for the weak and oppressed, especially women.

"Actually, I'm surprised the guys haven't taken advantage because there are so many single women," she said.

"There aren't many men, and a lot of them aren't particularly appealing."

Dr Hughes said growth among Pentecostals (such as Sydney's Hillsong Church) had been remarkable, along with ethnically based religions. For example, the Coptic Orthodox Church grew by 83 per cent between 1991 and 2001.

"Immigrants head to the churches in large numbers, even if they did not attend in their homelands," Dr Hughes said. However, he said he discounted fears in some church circles of mass conversions to Islam.

"The number of converts is very small, probably in the realm of less than a thousand or two. Only 2.5 per cent of all Muslims in Australia were born of Australian-born parents and some of these would be grandchildren of immigrants."

About 25,000 Australians identified themselves as Buddhist at the last census. Dr Hughes said young people liked its simplicity and ethics.

He said changes in immigration meant religion was now more diverse. Between 1996 and 2001, Buddhist numbers grew by 79 per cent, Hindus by 42 per cent and Muslims 40 per cent.

But all these groups together were still less than 5 per cent of the population.