The chief censor says a review of the accused Christchurch shooter's manifesto has ruled it was objectionable.
David Shanks said the Film and Literature Board of Review had confirmed that the document, called The Great Replacement, was objectionable.
The Board made its decision under the Films, Videos and Publications Classification Act following an application for a review.
The document was the manifesto of accused shooter Brenton Tarrant, and was banned because Mr Shanks said it crossed a line.
He said the decision sparked significant public debate as some felt it impinged upon freedom of expression.
"This is a document intrinsically bound up with... and relates to the most horrific event of mass murder we've ever seen in this country.
"This document promoted, encouraged and justified acts of murder and terrorist violence and from our assessment, and now from the assessment of the board of review, that crosses the line," Mr Shanks said.
He said while the screed would not have persuaded the vast majority of readers, it was not written for them.
"It was written for the small number of readers who are already on the pathway to violent extremism. Sadly, that small minority of readers could well be impressed by the example set by these vicious atrocities.
"They could buy into the document's justifications for acts of tremendous cruelty, and be inspired to target the areas identified for attack in New Zealand."
Mr Shanks said the aim of "hateful terrorist screeds" was to inspire others to similar violent action.
"Tragically, it appears that this may have already happened. Since March the 15th we have seen horrific extremist attacks unfold in a synagogue in Poway near San Diego, in a Walmart in El Paso and even more recently in a mosque in Norway.
"What we know so far about these attacks suggests that the attackers were inspired by the extremist ideology and justifications contained in The Great Replacement."
Mr Shanks said reports suggested the influence was evident in the killers' own documents and posts, posted immediately prior to the attacks.
He said an "effective response to this contagion" required an integrated strategy, and censorship was only one piece of the puzzle.
"All of us can make choices that might spread this dangerous hate further, or we can staunch its flow. Our choices matter, including those made by news media, online platforms and service providers, enforcement agencies, and the choices made by each of us as we interact and share, online and off."
The Great Replacement document was a banned publication in New Zealand, but exemptions had been granted to reporters, academics and specialists who were working on reports and studies for the purpose of informing the public in a considered way.