Health authorities are worried the new rules might make children fat by putting them off using their bikes.
They say rather than forcing kids to wear them, it would be better to make helmets "look fun and funky".
One cycling group says more people would die from the associated health risks of not exercising than the number who would be saved by helmets.
But Mr Martlew the MP says he wants bike helmets to become "as common as wearing a hat for horse-riding" because as many as 50 children die each year by not wearing them.
Hear story
Should kids have to wear bike helmets?
