A public health expert has called for laws making the wearing of bike helmets compulsory to be repealed, to encourage more people to ride bikes.

Australia became the first country to make riding without a helmet illegal in 1991.

Associate Professor Chris Rissel, from Sydney University's School of Public Health, says the greatest drop in head injuries was in the 80s - before the laws were introduced - because of road safety campaigns and speed controls.

He says the number of head injuries has remained steady since then, creating a case to overturn the helmet law.

"What it does is it puts people off cycling and makes people think that cycling's a dangerous activity, even though it's a really healthy thing to do and it increases people's physical activity," he said.

"And you're seeing things like in the Melbourne bike hire scheme - it's not working as well as it has in the rest of the world because people don't walk around with a helmet just in case.

"You've got helmets creating a barrier to cycling, particularly spontaneous, short-trip cycling.

"People who ride short trips down to the shops, or ride in parks or just going along quiet streets. Their risks are very, very low."

Bicycle New South Wales vice-president Richard Birdsey says road safety, not helmet laws, is the biggest turn-off for potential cyclists.

"At the moment it's important that we retain the law, but certainly once we see improved riding conditions for people, where the roads become safer, the governments should look at perhaps seeing whether they can be wound back a bit," he said.