The head of a conservative group is calling on families to boycott screenings of Fifty Shades of Grey and donate to a group like Women's Refuge instead.

Family First's Bob McCoskrie says the film and the book it's based on glamourise sexual violence.

He says families should boycott the movie and make a special donation to any charity that is working to eliminate sexual violence.

In New Zealand the censor's rating for the film is R18 with a warning it contains sex scenes and offensive language.