Australia should consider having a one-child policy to protect the planet, an environmental lobby group says.

Sustainable Population Australia says slashing the world's population is the only way to avoid "environmental suicide".

National president Sandra Kanck wants Australia's population of almost 22 million reduced to seven million to tackle climate change.

And restricting each couple to one baby, as China does, is "one way of assisting to reduce the population".

"It's something we need to throw into the mix," the former Democrats parliamentarian told AAP.

More people means more coal-fired electricity, cars, houses, water use and food production, all of which increase greenhouse gas emissions, she said.

Ms Kanck, who has one child herself, expects her campaign will receive a hostile reaction.

"The Catholic church is going to be in like Flynn on an argument like this."

Sustainable Population Australia, which has about 1300 members, is so worried about climate change it is preparing a formal submission to the United Nations.

It has also applied to attend high-profile world climate talks in Copenhagen in December.

Australia's population has been increasing steadily and the Federal Government plans to continue the trend, largely through immigration.

The world's population stands at 6.7 billion, according to the US Census Bureau.

"Increasing the population is basically suicide, it's environmental suicide, it's utterly irresponsible," Ms Kanck said.

"We are eating away at the planet, we are eating into all the resources, be it petrol, be it superphosphate, be it clear air."

Ms Kanck also suggested Australia scrap the baby bonus, and restrict paid maternity leave and IVF to the first baby only, to discourage large families.

She did not suggest restrictions to immigration, saying Australia should take responsibility for cutting its own population instead of barring entry to others.

China introduced its one-child policy in 1979.

A Chinese academic visiting Canberra last week said the policy had avoided 300 million births and had therefore made a major contribution to the fight against climate change.