Annette Brooke was third MP in a row to push for cycle helmet compulsion.
LibDem MP Annette Brooke is the latest MP to fail to get the UK Parliament to pass a bill forcing cyclists to wear helmets.
Previous private members' bills from MPs Peter Bone (Tory) and Eric Martlew (Labour) also failed to generate support from MPs.
The MP for Mid Dorset and North Poole presented her bill to Parliament in July but last week it failed to get a second reading.
In July she said the bill "aims to protect children from head injuries, and the devastating effects of brain injury, by making it compulsory for those under 14 to wear cycle helmets."
Children climbing trees, or travelling in cars, or walking on streets, or skateboarding, or riding kick-scooters, were not required to wear helmets in her bill, her proposed measure was just for cyclists.Article continues below
The Cycles (Protective Headgear for Children) Bill would have make it mandatory for children under 14 to wear cycle helmets when cycling on roads and in open spaces.
Brooke said: "The law will not criminalise those cycling without helmets, instead requiring proof of purchase of a helmet within 28 days to avoid a fine.
"We have a duty to protect our children, and the Cycles (Protective Headgear for Children) Bill will do just that. Brain injury devastates the lives of individuals and their families. Children are at a higher risk because not only are their brains not fully developed but they are less experienced at cycling and on the roads in general."
The MP has never introduced a private members' bill requiring measures to prevent the risk of cycling on roads, such as slowing down motorists.
"Brain injury lasts a lifetime. We owe it to children to protect them in the years before they are old enough to make their own minds up," said Ms Brookes.
"More children wearing helmets will mean a reduction in child deaths and serious brain injury. Through this Bill I hope we can make cycling even safer, and encourage children to get out on their bikes."
Forcing parents to make their children wear helmets reduces the demand for cycling, say anti helmet compulsion campaigners.
The MP's bill had the support of the BMA, brain injury charity Headway, the Bicycle Helmet Initiative Trust, Child Brain Injury Trust, road safety charity BRAKE, and the Child Accident Prevention Trust.
No cycling groups are in favour of cycle helmet compulsion. And Brookes did not have the support of key LibDem MPs. Julian Huppert, LibDem MP for Cambridge, and co-chair of the All Party Parliamentarty Cycling Group, said at the time of the bill's first reading:
"The Lib Dem transport team disagrees with her. I've tried to persuade her! Lib Dem (& coalition) policy is not to have compulsory helmets."