Christchurch mosque attacks: Royal Commission report may see heads roll over intelligence failure - expert

A leading international law expert says the findings of the Royal Commission into the Christchurch mosque attacks could talk of New Zealand's biggest intelligence failure yet.

The 800-page report will be released on Tuesday afternoon and some believe significant changes are ahead.

International law Professor Al Gillespie says heads may roll once the report comes out.

"If they were intentional oversights, if they were reckless oversights, or they were negligent in their duties, then you may expect to see some people have calls for their resignation," he says.

Other changes may include updated legislation in regards to the security services, firearms control, and also with police.

Prime Minister Jacinda Ardern is promising accountability and action, but won't confirm yet whether they'll offer an apology for failures that lead to the murder of 51 people.

"The recommendations span across a number of areas, they don't just relate, for instance, to security and intelligence agencies, and so it will take some time for us to implement some of the findings but some we'll implement quite quickly," she said on Monday.

The families and victims received the report ahead of its public release.

Survivor Farid Ahmed, whose wife Husna died in the attack, says the report is "very hard to digest emotionally".

He says the report puts the ball in the Government's court to act on its findings and make New Zealand safer than it is now.

"[There's] lots of expectations from people on Government."

But he hopes New Zealand will be a safer and better country as a result.

"I am very hopeful that the future is going to be safer for all NZ kids, all New Zealanders."