The chairman of New Zealand’s Royal Commission into the Christchurch Mosques attack has revealed interviewers sat down and interviewed the Australian terrorist as part of its work.

Justice Sir William Young has announced a face-to-face interview was conducted in private with Brenton Tarrant at Auckland Prison, Paremoremo, where the 29-year-old awaits his sentencing.

Sir William said the interview was conducted “to observe the principles of natural justice” and “there were some areas of uncertainty” following the provision of material provided by New Zealand Police and other agencies.

Another Commissioner, Jacqui Caine, said the decision to interview Tarrant was a “carefully considered decision”.

“We have given a commitment to the public that we would leave no stone unturned and interviewing the individual is another way we have sought to fulfil that commitment,” Ms Caine said.

Tarrant plead guilty to New Zealand’s worst mass shooting in March this year, 12 months after the attack, and was convicted of 51 counts of murder, 40 counts of attempted murder and one count of terrorism.

That decision has proved bittersweet for victims and the families of those killed in the shootings.

Tarrant’s plea reversal means survivors will not endure the pain of a lengthy trial, but equally, they will not be able to give evidence and get closure in the manner many were hoping for.

Without a trial, the Islamic Women’s Council of New Zealand is hoping the Royal Commission will publish the interview, or a transcript, in their report.

“For the country’s healing and for the healing of our community as well we need to see all the information and as much of what they gained in this interview that they can put into the report,” spokeswoman Anjum Rahman told Radio NZ.

Ms Rahman said she was surprised to learn the Commission conducted a face-to-face interview, and it should be seen as an opportunity to learn.

“We need to understand his motivations, his actions, how he went about what he did and how he escaped all notice to authorities,” she said.

“We didn’t get the full trial. All the evidence and all the information that would have come out at trial … I think the Royal Commission is the only avenue we have of getting that information.

“It needs to be shared with the wider public.”

It is unclear how the Royal Commission intends to use the information gained from the interview.

Tarrant is expected to be sentenced in August, while the Royal Commission must report to the Governor General by the end of next month.

-AAP