Family First is applying to the Film and Literature Board of Review to have the award-winning book, Into the River, re-classified for older audiences.
Into the River, by New Zealand author Ted Dawe, won the 2013 New Zealand Post Children's Book of the Year award.
Bob McCoskrie from Family First says the book contains explicit sexual content, highly offensive language, and references to illegal drug use and child sex exploitation.
He says the Office of Film and Literature's original classification was made by those with a vested interest in the book or its award.
Mr McCoskrie says Family First wants a warning on the book's cover and for it to be withdrawn from school and public libraries.
"We've also asked New Zealand Post to withdraw the prestigious award, it's just not appropriate to have an award sticker on the front saying it's the Children's Book of the Year."