Christchurch terror attack accused's mother blasts 4chan

The mother of the man accused of carrying out the Christchurch terror attack has lashed out at 4chan.

Sharon Tarrant said the website had jeopardised her only chance to correspond with her son, who is currently in solitary confinement at Auckland Prison.

"Other people with their own agendas are making it difficult for us to maintain contact with him. Like 4chan - it's about their ego. How dare they? They have taken away the right from me to hear from my son," she told NZME.

Newshub revealed on Wednesday a letter from Brenton Tarrant, who is accused of carrying out a shooting that killed 51 members of the Christchurch Muslim community on March 15, was posted on the controversial internet message board.

Much of his letter appears to be innocuous. However, it ends with what is effectively a call to action for like-minded people, which Newshub has decided not to share. 

Sharon Tarrant said she's thankful for corrections, who have been good to her family while her son is imprisoned.

"It breaks my heart to see the prison system being hammered when they have never had to deal with anything like this before," she told NZME.

"I want to thank the police who have kept him alive... Now they are being criticised it's really unfair."

Brenton Tarrant is facing 51 charges of murder, a further 40 of attempted murder and one charge of terrorism.

He's pleaded not guilty and will face trial in 2020.