A New Zealand children's author says priests should be able to marry and have sex.

Palmerston North bishop Charles Drennan resigned on October 4 after admitting inappropriate sexual behaviour with a young woman.

Joy Cowley says Drennan, who she considers a friend, did wrong but he didn't commit a crime.

She told Heather du Plessis-Allan priests in other countries have sex, such as the Phillippines and South America, because the culture is different.

"Here in the West, we tend to see church teaching as written in stone, where in other countries it can be the point of negotiation."

Cowley says that Drennan is being treated as though he has committed a crime.