Banned book Into the River can now be bought, borrowed and displayed after a decision by the Film and Literature Board to classify it as unrestricted.

The young adult book by Ted Dawe was given an interim ban after the Christian lobby group Family First complained about its content, which includes sex scenes, drug use and swearing.

In its decision, the board said although the book described a number of unacceptable, offensive and objectionable behaviours, it did not in any way promote them.

It said on the contrary, the book clearly set out to discourage and discredit such behaviours.

Mr Dawe told Checkpoint this afternoon he was no age restrictions were imposed.

"It's not so much the fact that 13-year-olds can't read the book, it means that it can't sit on the library shelves, it can't be handed around schools in the proper way and it creates a really alarming precedent for people that write."

Mr Dawe said today's unrestricted classification meant Into the River will go straight back on to library shelves, and his publisher was arranging a good supply of the book around the country.

The Board of Review decision for #IntoTheRiver has been registered: The book is classified as Unrestricted & can now be supplied to anyone. — ClassificationOffice (@NZOFLC) October 14, 2015

Limited stock of 'Into the River' is on the shelf now, and more will be winging its way to us ASAP. pic.twitter.com/kzcz5G0mkz — Unity Books WGTN (@unitybookswgtn) October 14, 2015

The Board said the history of the book itself was now almost as fraught as the story of its central character.

"There is no doubt that issues such as bullying, underage drinking, drug taking, and underage sex are very real, albeit undesirable, features of contemporary urban life…They are challenges which many of our school children will face and about which they will be required to make choices.

"The book focusses on the reality of those choices and the consequences of poor decisions, both individually and cumulatively.

"We consider the dominant effect of the publication will be to promote thought, discussion and debate amongst readers about real choices and issues that they and their colleagues are likely to have to confront," the Board said.

@rnz_news can I read some extracts on air? — Family First NZ (@familyfirstnz) October 14, 2015

However, in a dissenting opinion, the Board's President, Dr Don Mathieson, said he continued to believe the appropriate restriction is R18.

Dr Mathieson argued the passages depicting the book's sex scenes were gratuitously explicit.

"If they were planned to be read aloud as part of a radio play there would immediately be an understandable howl of protest, and they would be removed.

"Irresponsible sexual activity simply for pleasure should not be engaged in by any teenagers, particularly those as young as 13," he wrote.

Dr Mathieson said he regarded an R18 restriction as controversial, but was "in no doubt that a proper application of our current censorship law, which may or may not be out of date, requires the attachment of an R14 restriction to this publication at the very least."