A WEST Australian medical expert wants families to pay a $5000-plus "baby levy" at birth and an annual carbon tax of up to $800 a child.

Writing in today's Medical Journal of Australia, Associate Professor Barry Walters said every couple with more than two children should be taxed to pay for enough trees to offset the carbon emissions generated over each child's lifetime.

Professor Walters, clinical associate professor of obstetric medicine at the University of Western Australia and the King Edward Memorial Hospital in Perth, called for condoms and "greenhouse-friendly" services such as sterilisation procedures to earn carbon credits.

And he implied the Federal Government should ditch the $4133 baby bonus and consider population controls like those in China and India.

Professor Walters said the average annual carbon dioxide emission by an Australian individual was about 17 metric tons, including energy use.

"Every newborn baby in Australia represents a potent source of greenhouse gas emissions for an average of 80 years, not simply by breathing but by the profligate consumption of resources typical of our society," he wrote.

"Far from showering financial booty on new mothers and rewarding greenhouse-unfriendly behaviour, a 'baby levy' in the form of a carbon tax should apply, in line with the 'polluter pays' principle."

Australian Family Association spokeswoman Angela Conway said it was ridiculous to blame babies for global warming.

"I think self-important professors with silly ideas should have to pay carbon tax for all the hot air they create," she said. "There's masses of evidence to say that child-rich families have much lower resource consumption per head than other styles of households.

But the plan won praise from high-profile doctor Garry Egger. "One must wonder why population control is spoken of today only in whispers," he wrote in an MJA response article.