The Australian man convicted of killing 51 people in the horrifying shootings at two Christchurch mosque is appealing his convictions.

Brenton Tarrant is serving life sentences in a New Zealand for murdering 51 people and attempting to murder 40 others during Friday prayers at the mosques on March 15, 2019.

The sentences – a record in New Zealand – offered no possibility of parole.

He was also convicted in March 2020 for committing a terrorism offence.

A spokesperson for the New Zealand Court of Appeal confirmed on Tuesday that Tarrant had filed an appeal against his convictions and sentence.

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

A panel will hear an argument from Tarrant or his lawyers.

Tarrant was convicted in New Zealand’s worst terrorist attack, after killing 43 people at Christchurch’s Al Noor Mosque, and a further seven at the nearby Linwood Islamic Centre. He streamed his shooting attacks online, with the vision shared widely.

Tarrant had flagged a possible appeal about a year ago, under advice from Wellington-based human rights lawyer Tony Ellis.

Dr 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.

“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.”

Tarrant, who represented himself at his sentencing in August 2020, subsequently disposed of Dr Ellis’s services.

The Grafton, NSW, raised man’s decision to reverse his earlier pleas and confess his crimes came as a major surprise and meant the matter did not go to trial.

In October last year, chief coroner Deborah Marshall announced there an inquiry into the mosque attacks, saying it would allow a “more in-depth investigation into the causes and circumstances of the deaths”.

-with AAP