His concerns echoed New Zealand Prime Minister Jacinda Ardern, who has sought answers from agencies about how the Australian killer evaded attention by authorities, despite posting in online hate forums.

Mr Whish-Wilson did not receive any follow-up after reporting to the Australian Federal Police about the neo-Nazi posters stuck to the windows of his George Street office in February.

He said there was a feeling that "it wasn't being taken seriously", and was indicative of a failure to adequately police far-right groups.

"The fact that these right-wing terrorists slipped under the net in New Zealand, and one was an Australian citizen, shows there's been a failure at the Australian level as well," Mr Whish-Wilson said.

"We're going to have to reassess the importance of these groups now that we've clearly seen they have the capacity to commit an atrocious hate crime.

"Now that this has been labelled by the prime minister and others as a terrorist attack, I would expect the full resources of our intelligence agencies to investigate this in Australia.

"This didn't happen overnight."

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The day after his office was targeted, Mr Whish-Wilson questioned AFP Commissioner Andrew Colvin during Senate Estimates, who said he was personally unaware of the group named on the posters, Antipodean Resistance.

Mr Colvin said he was confident the protection liaison team was working "very closely" with Tasmania Police on the matter, and far-right extremist groups were on the radar of the AFP.

Other Australian politicians and university campuses were also targeted with Nazi propaganda at the time.

The AFP confirmed the man who carried out the Christchurch attack was not known to police.

Ms Ardern said New Zealand and Australian authorities would work together to find out how he slipped through.

"This individual should have been someone that the authorities were aware of and were proactively already focused on," she told the media.

"Those are the exact questions that we have asked and that the agencies are working on."

Far-right social media pages have continually been taken down in the past two years, but often re-emerge in other forms.

An Adelaide man was arrested and charged with firearms offences on Saturday after police were alerted to comments he had made on social media in relation to the Christchurch terrorist attack.