Tarrant appeals convictions and sentence

She said no date has been set for a hearing and grounds of appeal were not available.

The Australian man had pleaded guilty to planning and carrying out the 2019 massacre and was sentenced to a lifetime in prison without the possibility of parole.

In New Zealand media reports published a year ago, human rights lawyer Tony Ellis alleged Tarrant was "subject to inhumane or degrading treatment while on remand, which prevented a fair trial" in a memo to a coroner.

"He sent me about 15 pages of narrative of how he had been treated since he'd been in prison," Dr Ellis wrote in the memo.

"He said because of how he was treated while he was awaiting trial and afterwards, (that affected) his will to carry on and he decided that the simplest way out was to plead guilty."