Prime Minister Jacinda Ardern says it is "abhorrent and disgusting" that the alleged Christchurch terrorist's manifesto is being sold online.

But she says there is little New Zealand can do about it, as it is being sold in a jurisdiction where New Zealand holds no sway.

Neo-nazis are selling hardcover copies of the accused Christchurch mosque shooter's hate-filled manifesto online.

A far-right message board on an encrypted instant messaging site is selling the banned racist document for US$4 (NZ$6.23).

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"It's more than a concern," Ardern said today.

"It's abhorrent and it's disgusting, but it is being sold in a jurisdiction over which we have no control."

The copies are being sold on an online messaging app that was set up two days after the March 15 attacks.

The channel - which has more than 1000 subscribers - appears to be run by an administrator distributing the writings translated into Ukrainian.

New Zealand's chief censor has classified the manifesto as objectionable, meaning anyone found to be distributing it in this country could face up to 14 years in prison, or a $10,000 fine.

But that didn't mean the document was banned overseas, Ardern said.

"It wouldn't be able to happen in New Zealand, but this is, I understand, happening in the Ukraine. It demonstrates the difficulty we have now in this current environment in dealing with the spread of what we in New Zealand would consider really objectionable material."

She said that didn't meant the Christchurch Call, the voluntary agreement to stop violent extremism and terrorist content from spreading online, was a waste of time.

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"I don't think we should assume that just because an act doesn't fix everything that it's not worthwhile. The Christchurch Call will make a considerable difference, but it won't fix everything. It's not a reason not to keep going."

The channel features vile white supremacy messages, memes and videos and openly encourages violence against people of colour and Jews.

Its admin said he was inspired by the alleged killer and said he wants to "maximise the manifesto and everything related to it".

It is pictured alongside images of guns, Hitler, and the former Nazi leader's own anti-Semitic manifesto Mein Kampf.

On May 15, the administrator says he's working on printing out the document for widespread dissemination.

"I do not make money on this. If someone doesn't have shekels to spare — take the layout and print this out on your own, not a problem," the channel admin wrote.

"The idea is to give paper versions to everyone in a row, on birthdays, wedding anniversaries and baptisms of children. In the first place, the inhabitants, to open their eyes to our cruel world."

And on August 10, he boasts of sending eight books to new owners.

Last week, Corrections boss Christine Stevenson apologised for failing to withhold an inappropriate letter from the alleged gunman that was posted online.

Corrections also failed to block two inappropriate letters from Christchurch white supremacist Philip Arps, who is in jail for sharing the mosque shooting video.

Stevenson has put in a number of measures to prevent the mistake happening again.