The discovery has called into question whether bicycle helmet laws were enough for e-scooters, a researcher says.

The study spent four days counting the scooters in six locations across the Brisbane CBD and observed 45 per cent were being ridden illegally.

Users riding without properly wearing helmets is the most common unlawful activity.

It was found that 39 per cent of e-scooter riders had no helmet or wore a helmet that was not properly fastened.

Other illegal activity included riding on the road or carrying a passenger.

Almost 800 e-scooters were counted, 90 per cent of which were Lime shared scooters.

Users of private e-scooters were much better at wearing helmets with 95 per cent of users buckling up properly, says the QUT study.

Brisbane is the Australian city where the Lime first launched the share scooters.

The company announced recording a million rides in its first six months of operation in June.

Professor Narelle Haworth, who published the results of the study in The Medical Journal of Australia, says the study called for further research into whether bicycle helmet standards are adequate for e-scooters.

She said there was a need to ensure helmets remain available and there was enough police enforcement of helmet rules.

"Further research is needed to investigate whether the current bicycle helmet standards are adequate for e-scooters," Professor Haworth said in a statement.

Australian Associated Press