Prime Minister Jacinda Ardern says there will be a royal commission of inquiry into the Christchurch terror attacks, which left 50 people dead after a shooting at two mosques.
It will look into the accessibility of semi-automatic weapons, social media and security services.
"The inquiry will look at what could have or should have been done to prevent the attack,” Ms Ardern said after Cabinet agreed on the inquiry.
"It will inquire into the individual and his activities before the terrorist attack, including a look at agencies. It will look into the actions of the SIS, the GCSB, police, customs, immigration and any other relevant departments or agencies.
She said there would be a focus on if the intelligence community "was concentrating its resources appropriately and whether there were any reports that could of or should of alerted them to this attack".
"It is important no stone is left unturned."
Ms Ardern wanted recommendations of how any attack in the future can be stopped.
The royal commission is appointed by and reported to the Governor-General, and is then presented in Parliament.
The inquiry lead and duration will be announced in the next two weeks.
Ms Ardern made the announcement last week that an inquiry into the circumstances leading up to the terror attack would take place.
She said at the time it would include looking at any intelligence sharing challenges, and also the suspect's travel, social media and interactions with others.
The options were between a royal commission, public inquiry or a ministerial inquiry, with the latter allowing for more ability to manage timelines and classified information.
National's Simon Bridges yesterday supported a royal commission of inquiry into New Zealand's security and intelligence agencies.
This morning Mr Bridges told TVNZ1's Breakfast hard questions need to be asked.
"That's why in the last day I've called for a royal commission, that's reserved for really important things and what’s more important than this and New Zealand's safety."