SYDNEY - Five years ago, an Australian man read some news articles about himself on Facebook and came across a series of allegedly defamatory comments posted by users beneath the articles.

Mr Dylan Voller had been in the news because his mistreatment at a youth detention centre had made national headlines and sparked a royal commission.

After reading the comments on Facebook, Mr Voller did not sue the people who posted them, or Facebook, but instead sued the media companies whose Facebook pages featured the articles.

In a controversial 5-2 ruling in September, the High Court found that the media companies were legally responsible for third parties' comments on their Facebook pages. This effectively means that they must either monitor every comment beneath every article on their social media sites, or ban user comments on all stories, or stop posting stories altogether.

Following the court ruling, CNN blocked access to its Facebook pages in Australia, and other publishers in Australia disabled or restricted comments. Some MPs have also disabled comments on their Facebook pages.

A scathing editorial in The Australian newspaper last month said: "To push responsibility for third-party defamation on to news outlets defies logic and ignores the realities of the modern world."

The case has sparked fresh debate in Australia about its notoriously strict defamation laws, which have led to the country being described as the "defamation capital of the world".

There have been a series of prominent defamation cases that resulted in staggeringly high payouts. Oscar-winning actor Geoffrey Rush was awarded almost A$2.9 million (S$2.9 million) in damages in 2019 over articles published by Sydney's The Daily Telegraph in 2017. Actress Rebel Wilson was awarded A$4.7 million in a case against a magazine publisher, though the amount was reduced on appeal to A$600,000.

These cases added to calls by a mix of journalists, media outlets and lawyers to overhaul the defamation laws, which have been described as the most repressive in the English-speaking world. The laws make defending defamation cases difficult and costly, leading to media outlets and journalists avoiding publishing on sensitive topics or figures.

Australia's politicians have often been reluctant to change the defamation laws, partly because - as public figures - they have tended to favour access to strong tools to defend their reputation. MPs regularly launch or threaten defamation suits against reporters and media outlets.

But there have been growing calls among MPs to review the laws, particularly to ensure they are consistent with new technologies.

Federal Attorney-General Michaelia Cash last month wrote to the states and territories to call for nationally consistent changes to Australia's defamation laws in the wake of the Dylan Voller case.

"Our work to ensure that defamation law is fit-for-purpose in the digital age remains critical," she wrote.

State and territory lawmakers have begun reforming the legislation, but progress has been slow. Defamation law is controlled by individual states and territories, though all agree that a consistent national approach is needed.

In July, several states changed their defamation laws to try to add clarity and encourage parties to settle. The changes include a requirement that aggrieved parties must notify the other parties of their "concerns" before they can sue. In addition, aggrieved parties must now show that the defamatory material caused "serious harm" to their reputation - a measure designed to avoid insignificant lawsuits.

The states and territories are considering a further set of changes, which could include laws to prevent media outlets and others from being sued for third-party user comments on social media that were beyond their control. The changes could also reportedly include treating Facebook and other social media giants as publishers - rather than platforms - and making them liable for defamatory content.

Significantly, Prime Minister Scott Morrison has led a global push to rein in the power of social media giants and has signalled support for making them more responsible for content that appears on their sites.

He said last month that he wanted to ensure technology was not enabling abuses of free speech.

"The lack of accountability that sits around it is just not on," he told reporters. "You can expect us to be leaning even further into this."