A second letter sent from a New Zealand prison containing extremist views was sent by white supremacist Philip Arps, Corrections has confirmed.
On June 18, Arps was sentenced to 21 months jail for sharing footage of the March 15 terrorist attack on Christchurch's Al Noor mosque.
It comes after Wednesday night it was revealed that a letter written by the man accused of killing 51 people in the Christchurch terrorist attack was posted to the far-right message board 4chan.
Corrections Department chief executive Christine Stevenson said late yesterday afternoon, it was brought to her attention that a second letter from a prisoner holding extremist views has been sent out of Christchurch Men’s Prison.
"This is totally unacceptable, it should not have happened, and I apologise for any further distress this has caused," Ms Stevenson said.
"I do not have confidence in our existing processes for reviewing and assessing of prisoners’ mail, and I have called for an immediate review into this practice.
"I want to reiterate my unreserved apology for the distress that this has caused to those impacted by the tragic events of 15 March. We take our responsibility for safety very seriously, and on this occasion we have not met our own high standards."
Ms Stevenson said she had briefed Corrections Minister Kelvin Davis on what will happen immediately, including the mail of prisoners who have been identified with extremist ideologies and/or registered victims will be immediately centralised pending a full review carried out by an external party. That party is yet to be determined.
She said it will remain this way until the review has concluded and she is confident the new process in place will prevent this from happening again.
"This has also highlighted the need for us to look at the current legislation and how it is being applied and whether it is fit for purpose," Ms Stevenson said.