An 0800 number has been set up for people who receive unsolicited letters from prisoners following revelations Corrections allowed hate-filled letters to be sent.
Corrections chief executive Christine Stevenson announced the 0800 number and email address on Monday, so people who receive letters they don't want have somewhere to go.
People can now contact 0800 345 006 or email firstname.lastname@example.org if they receive correspondence from prisoners they don't want.
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It follows Newshub's revelation that the alleged Christchurch massacre gunman Brenton Tarrant was able to send seven letters from prison, one which appeared to have a call to action for likeminded people.
Multiple letters were also sent from Philip Arps, another white supremacist who was jailed for sharing Tarrant's livestream of the March 15 shooting.
Corrections has admitted that the letter seen by Newshub - in which Arps expressed his support for Adolf Hitler and openly talked of his disdain for the Prime Minister - should never have been sent.
"We will have to be more vigilant... I apologise sincerely for the distress this has caused... Public safety is at the heart of what Corrections does and we failed our own high standards last week," Stevenson said.
"I have now announced that I will be signing out any correspondence from the particular prisoner but I've also centralised all the mail from those most risky prisoners with extremist views."
She said Corrections receives at least 15,000 items of mail leaving prisons every week, and that "there will be things that may slip out that we're not aware of".
"So if there's a 0800 number to be called, there's an email address, then people can reach out to us and we can put a stop to it."
The Prime Minister's office has told Newshub changes to the mail system will be considered by Cabinet on Monday.
"I think it's well overdue... We're taking steps to address it," Corrections Minister Kelvin Davis said on Monday.
"We've established the 0800 number but we're going to be looking at the mail system in general in prisons because at least as far back as 2010 it hasn't been working the way it should."
Stevenson said the law "could be made a little bit clearer so we've been talking to the minister about that and we'll see what he minister wants to do".
She said two academics have agreed to help with ideas.
National leader Simon Bridges said Davis' job is to ensure that Corrections had the procedures in place to deal with Tarrant, accused of murdering 51 people.
He said Cabinet would be wasting time discussing whether the laws around letters being sent from prison are good enough.
"Instead of Cabinet sitting around talking about this today, they should save some time and focus on ensuring the laws that are in place are followed properly.
"It's time for Kelvin Davis to get on and do his job."
Prime Minister Jacinda Ardern, who has vowed not to speak Tarrant's name, said last week there had "clearly" been a "systemic failure" in that he was able to send letters to his supporters.
"Now we have to make sure that the department is going back and checking their systems, and equally that we're checking the law."
The Corrections Act states that a prison manager may withhold mail between a prisoner and another person if it could "endanger the safety or welfare of any person".