A controversial report claiming helmets increase cyclists' injuries has been rubbished by experts.
The Evaluation of New Zealand's Bicycle Helmet Law report published in today's New Zealand Medical Journal also says forcing cyclists to wear helmets has contributed to 53 premature deaths each year and halved the number of cyclists on the roads.
But an academic and cycle advocate have separately said it was "a stretch" to say the helmet law, which came into effect in 1994, was solely responsible for those findings.
In the report, UK cycle coach Colin Clarke, compiled numerous New Zealand sources to question whether a mandatory cycle helmet requirement was the "best approach to promoting health and safety".
Mr Clarke claimed cycling use had reduced by 51 per cent since the helmet law was passed.
In the period from 1989 to 1990, before the law was imposed, the average New Zealander spent 11.4 hours per million cycling.
But 10 years later, for the period 2006 to 2009, New Zealanders only spent 5.6 hours per million on a bicycle.
Head of the University of Auckland's School of Population Health, Professor Alistair Woodward, said numerous other factors would have contributed to that reduction - not just the helmet law.
"It is true that cycling became less popular in the period after the law was introduced. But many things changed at that time, for instance, cheap secondhand cars became available. It is difficult to attribute the changes in cycling to any one factor," he said.
Mr Woodward also noted there had been an increase in cyclists despite no change in helmet requirements.
In his report, Mr Clarke also concluded that since helmet law came into effect 20 more cyclists were being injured per hour.
"Cyclist safety has been reduced due to the helmet requirement and law," Mr Clarke concluded in the report.
However, he found the number of cyclist deaths per hour had decreased by 11 per cent.
Cycle Action spokeswoman, Barbara Cuthbert, said she "struggled" with Mr Clarke's conclusion.
"So many things have changed since that law went through - there are far more cars on the road, younger drivers and so many other factors that have resulted in increased cyclist injuries ... this is just so leftfield.
"And in terms of saving us from brain injuries, [wearing helmets] has been significant," she said.
The report states that as well as reducing cyclists' safety, the helmet law has been blamed for reducing public health.
Mr Clarke estimated the helmet law has contributed to 53 premature deaths per year due to reluctance to cycle and therefore less people exercising.
"Making cycling less convenient and with the potential for parents to incur a fine if their child is not wearing a helmet could add to the discouraging effects due to legislation. The helmet law actually reduced public health," Mr Clarke stated.
Mr Woodward said he agreed the health benefits of cycling were much greater than the risks of crashes and injuries and cycling should be encouraged.
"But I am not persuaded that withdrawing the helmet legislation would boost the numbers of people cycling. There are other steps we can take and I think this is where the priorities lie."
Mr Woodward said for example, more bike paths and bike lanes, safer intersections and lower vehicle speeds in shared spaces would help boost cyclist numbers.
"And there is no doubt at all that if you fall or are knocked from your bike and strike your head on a firm surface, your brain is much better off inside a helmet."