Alleged Christchurch shooter Brenton Tarrant sent seven letters from prison

The man accused of the Christchurch mosque attack has been able to send seven letters from prison.

On Wednesday, Newshub revealed that Brenton Tarrant was able to send a six-page letter to a Russian supporter.

Corrections Minister Kelvin Davis has now admitted that wasn't the only one. Tarrant has tried to send nine letters while in solitary confinement, two of which were withheld.

He successfully sent two to this mother and five to unknown recipients.

Davis told The AM Show he's disappointed with the mistake and has received an apology from those responsible.

"We know that a mistake has been made," he says.

"Public safety is our number one concern, both here in New Zealand and overseas."

He says five of the letters were responses to "unsolicited mail from around the world" which had been screened by Corrections. There has been a co-ordinated effort from users on the anonymous message boards 4chan and 8chan to bombard Auckland Prison with fan mail for Tarrant, who is revered in some online white supremacist communities.

There have also been a number of copycat attacks in other countries since March 15, with multiple suspects citing Tarrant as a direct influence.

Tarrant's letter to Russia, which was posted on 4chan on Tuesday, contained what seems to be a direct call to action to his white supremacist fanbase.

Davis says he's questioning whether New Zealand's laws are fit for purpose and is seeking advice from Corrections on a potential law change.

"We've never dealt with a prisoner like this before."

Inmates in New Zealand prisons are entitled to send and receive mail, a practice the Minister has put on hold while the situation is assessed.

When AM Show host Duncan Garner said Corrections staff had been negligent, Davis said the problem was systemic.

"There is a process and the process has failed. We admit that and we've got to make sure it doesn't happen again."

Massey University law professor Chris Gallavin says Davis blaming the system rather than individuals is "classic deflection".

"This is a very particular, specific issue," he told the AM Show. "He's trying to make it much, much bigger to avoid the obvious which is that there's been a stuff-up."

He says there's nothing wrong with the current law around prison mail, which allows staff to withhold any mail coming in or out, and it doesn't need to be reviewed.

However, he says stopping all mail would be going too far.

"If he wants to write to his mother or his parents about things that are completely innocuous, then we should absolutely let him. He has some rights and they're there for a good reason. What he can't do is have a platform and stage to spew his vitriol or promote criminal activity."

Gallavin says Tarrant is worshipped as a hero by some, and New Zealand has contributed to that by allowing him to get letters out.

"It would be laughable if it wasn't so serious. We look like a bunch of idiots."