The Royal Society for the Prevention of Accidents advocates the use of cycle helmets, but would only support compulsion if enough people were already wearing them to make the law enforceable. There isn't.
BRITISH MEDICAL ASSOCIATION
Extracts from the BMA report of 1999 on cycle helmets:
[Much] of the literature on child cycling takes an adult-centred approach leading to the idea that children should protect themselves with helmets, and are to blame if they are injured. However, children should have the freedom to cycle in safety, and to achieve this requires a change in the behaviour of adults, rather than "suits of armour" for children.
Current helmet wearing rates in the UK are low and consequently, as occurred in countries such as Australia, extensive helmet promotion would be needed in order to raise awareness and wearing rates prior to the introduction of any legislation. Focussing on cycle helmets as the answer to reducing cycle accidents could detract resources from other more effective means of accident prevention. Cycle helmets...are only designed to protect the head during low speed impacts, (e.g. 13 mph) such as would occur in a fall to the ground from a bicycle, rather than in an impact with a motor vehicle.
An individual who wears a helmet by choice may be more selective about the quality of helmet purchased and take the time to fit it correctly, than someone wearing a helmet only to comply with legislation and avoid prosecution. This is should be taken into account in any consideration of compulsory helmet legislation.
NATIONAL CYCLING STRATEGY BOARD
Philip Darnton, acting chair of NCSB, said helmet compulsion "would dramatically reduce the number of cyclists and, as such, be the worst possible step to take when we are also concerned about the desperate health problems arising from obesity."
DR KIM HOWELLS
Howells, MP for Pontypridd, has been an active cyclist since the 1950s, and started wearing a cycle helmet five years ago. "But it's my choice," he said.
"There needs to be a damn good reason to bring in legislation. I am very, very much aware of the arguments on both sides, and in the middle. I think the Martlew bill will get wide, cross-party support in the House so the Government's position is critical. The official line is that we are currently considering the balance of arguments. My own feeling is that it would be very difficult legislation to enforce by the police. I can't even get my own kids to wear helmets."
Other groups against Martlew's Bill are Transport 2000, road victims charity Roadpeace and Move4Health, which campaigns to get people more active, more often.