Cllr Rosenstiel, who represents Market ward on Cambridge City Council and is a member of Cambridge Cycling Campaign, took safety teams from Cambridgeshire County Council to task at a Guildhall meeting.
He said: “There is some academic evidence that if you are wearing a cycle helmet, you are at an increased risk of being in an accident.
“The concern is that there are a number of people, not just at the county council, trying to compel users to wear them – the county council, for example, has banned any publicity which doesn’t show cyclists in helmets.
“There is some evidence that it puts people off cycling and into more dangerous modes of transport.”
Cllr Rosenstiel’s declaration is backed by 2006 research from Bath University, which found motorists tend to pass cyclists wearing helmets more closely than those who are not.
Last month, cycling instructor Simon Nuttall slammed the county council’s “obsession” with helmets, warning the headgear might encourage complacency. He told the News the best thing riders could do was to improve their confidence and get good training.
Cllr John Reynolds, a member of the county council’s cabinet, sits on the same group as Cllr Rosenstiel – the Cambridge traffic management area joint committee.
Afterwards, he told the News: “The council believes the wearing of cycle helmets substantially reduces the risk of injury when a cyclist is involved in an accident.