Conservative lobby group Family First is considering its legal options after a ban on controversial teen novel Into the River was lifted.
An interim restriction order was applied last month on Ted Dawe's award-winning coming-of-age novel making it illegal to sell or supply the book anywhere in New Zealand.
Film and Literature Board of Review took the step after Family First sought to have an age restriction placed on the book because of its subject matter.
The book contains offensive language and addresses several controversial issues, including having sex under the legal age, illegal drug use, child sex exploitation and violent assault.
In a 4-1 majority decision the board lifted the ban saying it did not believe an age restriction was justified.
Family First national director Bob McCoskrie said the group would be writing to the board with concerns over whether due process was followed in its decision.
Of particular concern was the fact the Classification Office originally recommended an R18 rating.
He accused the board of bowing to book industry pressure to remove the restriction.
"The focus is not so much on the book, it's on the process and giving confidence to parents that a vetting system is working properly."
While the group did not intend to appeal the lack of age restriction on Into the River, he said the move set a "dangerous precedent" for the release of similar material.
"We want the board to get their standards right," he said.
The board said there were aspects of the book that may offend and may be regarded as inappropriate for children.
"Whilst many parents may choose not to allow their children to read such material, there are no grounds to restrict the book from teenage readers," it said.
Author Ted Dawes said he was "thrilled" at the board's decision.
"It has restored my faith in New Zealand's legal system."
The book has been embroiled in a back-and forth censorship battle since controversially taking out top prize in the 2013 NZ Post Children's Book Awards.