Forcing cyclists to wear helmets would be "a public health disaster" Exeter MP Ben Bradshaw has warned.
The former Health Minister and himself a keen cyclist and said he cared deeply about the safety of bike-riders, but argued the compulsory measure would be counter-productive.
Other countries which had made cycle helmets have been made compulsory including Canada and Australia, had seen useage plummet, with a resulting negative knock-on effect for health.
Mr Bradshaw was responding to calls by a Conservative MP for cycle helmets to be made compulsory for children.
Alok Sharma said the safety benefits of helmets for children were clear and the Government should legislate to make them mandatory.
But Road Safety Minister Stephen Hammond told the parliamentary debate that while he was keen to strongly promote the use of helmets he would not support changing the law.
Mr Sharma acknowledged calling for compulsory helmet laws would be 'controversial'.
But he said: "The statistics on serious injuries to cyclists bear out why a cycle helmet is so important, especially for children."
Mr Bradshaw said he backed a range of measures to improve cycling safety, but this stopped at making the wearing of helmets compulsory, and called on those arguing for it to study the evidence.
He said: "I speak as a lifelong cyclist, a former chairman of the all-party group on cycling, a former Health Minister and someone who cares deeply about the safety of cyclists and young cyclists in particular.
"Wherever cycle helmets have been made compulsory - whether in Canada, New Zealand or Australia - that has had such a detrimental impact on cycling rates that the overall impact on children's health and the health of society as a whole has been deeply negative.
"By all means encourage, by all means exhort and by all means have campaigns, but please do not, based on the best intentions, pursue a policy that is deeply counter-productive and that will cause more premature death, more obesity and more ill health among young people.
But Mr Hammond added: "We do accept this is a matter of (promotion) rather than compulsion.
"I agree anything outside of legislation which can promote wearing of cycle helmets, I will do."