If social media giants can build algorithms to sell ads, Scott Morrison says they can find ways to stop terrorists spreading horrifically violent videos.
The prime minister wants G20 nations to consider practical ways to force companies like Facebook and Google to stop broadcasting atrocities and violent crimes.
NSW man Brenton Tarrant has been charged with murder following the shootings at two mosques in Christchurch which killed 50 people and left another 50 injured.
The attack was live-streamed on Facebook, but none of the 200 people who watched it live reported it using the company's content reporting tools.
"If you can write an algorithm to make sure that the ads they want you to see can appear on your mobile phone, then I'm quite confident they can write an algorithm to screen out hate content on these social media platforms," Mr Morrison told reporters in Adelaide on Tuesday.
Opposition Leader Bill Shorten agreed.
"I do not believe it is beyond the technological capacity of some of the richest, largest, most powerful, cleverest, most sophisticated businesses in the world, not to be able to better monitor the material before they publish it," he told reporters in Western Australia.
Facebook vice president Chris Sonderby confirmed the company has to wait for users to report horrific content, but once it has been reported the company can automatically block people from uploading it again.
New Zealand Prime Minister Jacinda Ardern said social media companies must take responsibility for what they publish.
"They are the publisher. Not just the postman. There cannot be a case of all profit no responsibility," she told parliament.
Mr Morrison wrote to G20 2019 president, Japanese Prime Minister Shinzo Abe, calling for agreement on "clear consequences" for social media companies.
Tarrant, 28, was not on any security watchlist in Australia or New Zealand, despite online profiles linked to him containing material promoting white supremacist views.
Facebook took down 1.5 million copies of the footage and authorities were last week left scrambling to stop its spread across the internet on Twitter, Google and elsewhere.
Telstra, Optus and Vodafone have blocked a number of websites for continuing to host the massacre video.
Social media expert Damien Spry, who lectures at the University of South Australia, said Facebook had struggled to cope with the popularity of its live broadcasts.
"Once it is uploaded then it's almost impossible to take it down before it at least gets spread to a few other users," he told ABC Radio National.
Greens leader Richard Di Natale said debate about social media should not be used to absolve politicians and mainstream media from their responsibility not to fuel hate speech.
Australian Associated Press