"It's exposure to unnecessary risk. Why would you put an 8-year-old girl in front of naked men?"
Mr Bell said 8-year-olds were too young to know what was right and wrong.
"Children don't have the capacity to make an informed decision. It's the responsibility of the adult to make sure they are in a safe environment."
Bob McCoskrie, Family First's national director, was against the New Zealand World Naked Bike Ride taking place and concerned to hear an 8-year-old had been part of it.
"When you're getting 8-year-old kids being exposed to that stuff you have to think something's wrong. Most people would agree with that," Mr McCoskrie said.
"Most people would be concerned to have young children being exposed to full frontal nudity."
When asked what he would tell the girl's mother if given the opportunity, Mr McCoskrie said: "What adult wants to expose an 8-year-old girl to full front nudity?"
The event's organiser, Andrew Pointon, said children had been involved in the event all over the world.
So when the girl's mother contacted him to ask if her daughter could also ride, he said yes.
"It's about your body image and nude is not rude, so why should children be eliminated," Mr Pointon said.
"It's not a ride to segregate age or gender or anything else," he said.
"I don't like people singling out children for being naked because it seems perverted.
"It doesn't faze me and it shouldn't faze anyone else.
"The little girl had permission from her mother and they had a wonderful time," Mr Pointon said.
