A High Court Judge has ruled that cyclists injured in accidents are partly to blame for their injuries if they are not wearing a helmet, even if the accident was not their fault.

The ruling which has upset the cycling world could see cyclist accident injury compensation claims reduced by around 15% even when the accident was through no fault of their own.

Many believe it is the beginning of measures to force cyclists to wear helmets, with the Mayor of London, Boris Johnson believing riders should have the right to choose "hatless, sun-blessed, wind-swept liberty" or "helmeted security".

Commenting: “In my efforts to do the right thing I have ended up giving offence to both opposing factions,” he said, “As soon as I started wearing a helmet I was denounced as a wimp. As soon as I was pictured not wearing a helmet, I was attacked for sending out the wrong signal.”

The judges ruling follows a case brought after a cyclist, Robert Smith was riding to a friend’s house in Brightlingsea in Essex in 2005 without a helmet, when he was in a collision with a motorcycle ridden by Michael Finch.

Mr Smith was near the centre of the road ready to turn right, when Mr Finch who was driving at excessive speed, attempted to pass on the offside. They were involved in a collision and Mr Smith suffered a serious brain injury as a result of the accident.

The judge concluded that Mr Smiths head hit the ground at more than 12mph so a helmet would not of made any difference but said: “There can be no doubt that the failure to wear a helmet may expose the cyclist to risk of greater injury”, adding subject to limitations, “any injury sustained may be the cyclist’s own fault”.

This ruling could affect cycle accident compensation claims if the 'contributory negligence' principle is picked up by insurers where the rider is not wearing a helmet.

Evidence from Western Australia suggests helmets may not reduce cycle accident head injuries. When helmets were made compulsory there, cyclists dropped by around 33%, but head injuries dropped by only 10%.

The British Medical Association (BMA) believe helmets should be compulsory for cyclists saying: “Doctors working in accident and emergency see at first hand the devastating impacts cycling injuries can have.”