A shake up is on the cards at Corrections after a Christchurch man who once delivered pig heads to the Al Noor mosque was allowed to send threatening letters.
As well as mail from the alleged mosque shooter, letters from well-known white supremacist Philip Arps were also allowed out.
Corrections chief executive Christine Stevenson told Mike Hosking they've let everyone down by allowing the letters, which contained threats against the Prime Minister to be sent.
She says the system will be changed.
"There is a new team which will screen all mail from prisoners identified as having extremist views.
"All correspondence sent to and from the accused will now be personally checked by me."
Stevenson they had a lot of meetings about dealing with prisoners like him in the aftermath of the mosque shootings.
"I don't know how they slipped through the cracks. We have let New Zealanders down, but I am still proud of my staff and the work they do."