The Royal Commission into the March 15 terror attack has stamped 30-year-long suppressions on evidence given by ministers and senior public servants raising concerns that accountability may be dodged.

The commission's report, which will be released by the Government on Tuesday, December 8, is expected to detail any failings within government organisations, including police and the spy agencies, in the lead up to the terror attack – including how the terrorist obtained a firearms licence.

Among the widespread suppression rulings made by the commission are the permanent suppression of the police staff involved in granting the Australian-national a firearms licence, including the two people who vouched for the terrorist.

Stuff has previously reported on police's failure to properly scrutinise the terrorist, wrongly licencing him to purchase the stockpile of semi-automatic guns later used to murder 51 people.

Islamic Women's Council national coordinator Anjum Rahman was concerned the suppression of evidence given by ministers and chief executives, in particular, might prevent accountability for negligence, wrong-doing, and incompetence.

She said a coroners' inquest into the terror attack may be required if accountability was obstructed.

“That’s a concern. There needs to be some kind of accountability ... if this royal commission process can’t deliver that ... the next step has to be a coroners' inquest.”

She said she remained frustrated at the commission's process, which prevented the evidence put forward by government agencies from being contested.

“We still, and have continually, expressed our frustration that we weren’t able to hear what these agencies have said, or challenge their information.”

The suppressions were noted in the final minute from the commission, published after it the report was handed to Internal Affairs Minister Jan Tinetti on Thursday. Tinetti later confirmed the report would be made public on Tuesday, December 8..

The commission, Supreme Court Judge Sir William Young and former diplomat Jacqui Caine, determined an interview with the terrorist would be permanently suppressed because of concern it would be used by others to plan attacks and further spread the terrorist’s views.

Also, permanently suppressed was evidence and documents provided by government agencies, including classified material. This was to prevent the material being used as a “how to” manual for terrorists, and to maintain the confidentiality of people who spoke to the commission.

“We told them that our process was private ... We did this with a view to encouraging candour, which we received,” the commissioners wrote.

The commissioners decided the evidence provided by Government agency chief executives and current and former Cabinet ministers should be suppressed for 30-years, allowing public release in the future when national security concerns “dissipate”.

“Historians and others will have a legitimate interest in understanding in due course what those officials and former and current ministers had to say to a Royal Commission like ours.”

The commission also ruled that the identity of certain witnesses would be suppressed, including the two people that acted as references for the terrorist in his firearms licence application: “the gaming friend”, and “the gaming friend’s parent”.

It is the first official confirmation that the terrorist's references were provided by a friend and his parent. The firearm licensing process requires family members to provide a character reference.

Police staff involved in the licence application, including a former Dunedin arms officer, firearm licencing clerk, vetting officer, and Waikato vetting officer, would also have their names suppressed.

Stuff has previously reported that it appeared police failed to properly vet the terrorist when granting him a firearms licence. Sources, who required anonymity to speak, said police relied on character references, a father and son, who met the terrorist through an Internet chatroom.

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The commissioners said they were concerned for the wellbeing of both the Waikato father and son and the police staff, noting all had been “subject of considerable media speculation”.

“Publication of their names is not necessary for the public to understand what happened.

“We have reached conclusions on the firearms licensing system, and the processing of the individual’s firearms licence application ... We are satisfied that each one of them [police staff] acted in good faith.”

Submissions made by the Human Rights Commission, the privacy commissioner, the current and former race relations commissioners, the ombudsman, and the auditor-general, would not be suppressed, the commissioners said.