Privacy Commissioner John Edwards is calling on Facebook to give the names of anyone who shared the livestream of the mosque shootings to police.
The livestream appeared and spread quickly on Facebook on Friday. The company said it removed 1.5 million copies of the video in the 24 hours after the attack.
Mr Edwards said it was irresponsible for the social network to offer livestreaming if it could not detect and prevent abuse of the feature in a timely manner.
"Facebook should be notifying the police of the account names of the people sharing this content" - John Edwards
Mr Edwards said sharing of graphic content was a predictable risk of a livestreaming feature.
"It's absolutely inexcusable to offer something with these kind of threats without the ability to detect and prevent that kind of abuse in a timely way."
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"They invest enormously in creating algorithms to sell us things," he added.
"They should have caught this before it had to be drawn to their attention by the police."
Mr Edwards said Facebook should be notifying police of the account names of the people sharing this content.
Doing so did not pose a privacy issue "because at the core there is a very egregious offence to the rights and privacy of the victims", he said.
More than 50 New Zealand companies are considering pulling ads from Facebook to try to force the company to act.
Some firms have already stopped advertising and the Association of New Zealand Advertisers predicts dozens of others are likely to follow suit.
Association chief executive Lindsay Mouat said Facebook and Google were big but were not the only advertising platforms.
Mr Mouat said Google, as owner of YouTube, had previously responded to economic pressure over a child exploitation scandal on YouTube.
NetSafe director Martin Cocker said Facebook had removed the mosque video remarkably quickly.
"I know that the 17 minutes was way too long because of what is in that video and the way that that video was distributed but the reality is the time that it took to get that video down is remarkably quick. I'm not saying it's fast enough to reduce the harm," he said.
"It's very difficult to isolate offenders very quickly" - Martin Cocker
"Cyber crime is incredibly hard to counter. It's a big internet out there with a lot of people doing a lot of things and it's very difficult to isolate offenders very quickly and take action against them very quickly.
Belinda Barnet, senior lecturer in social media at Swinburne University of Technology in Australia, said social media networks were excellent at removing content from the Islamic State and other extreme groups - but did not deal with white supremacists in the same way.
The platforms had the tools to crack down on hateful and racist comments, and could monitor content using including algorithms, community watchdogs, and moderators, she said
Offensive comments were echoed by people in positions of power, which entrenched the position of extreme groups, Dr Barnet said.
"We need media and community pressure to take right-wing extremism seriously - it needs to become an illegal activity."
Dr Barnet said networks also received revenue from promoting speakers such as Milo Yiannopoulos.
The far-right figure has been banned from entering Australia following his comments on the mosque attacks which the country's immigration minister described as fomenting hatred and division.
Meanwhile the darker side of the internet is ignoring requests by the police to preserve online data linked to the accused gunman.
Links to a livestreamed video of the shooting were posted on two websites RNZ has chosen not to name.
A copy is being actively advertised for download on one of them.
Police have confirmed they've made contact with the site and, pending a formal legal request, have asked it to preserve posts, as well as IP and email addresses linked to these posts.
The site's owner responded with an expletive-ridden refusal to comply.