Two days of hearings on a challenge to Australia's landmark social media ban for children will begin at the country's highest court on Tuesday.

In a major test of the world-leading policy, a digital rights group will argue that the ban for under-16s robs children of their right to free communication. A separate challenge launched by platform Reddit will be jointly heard.

Introduced last December, the ban is a key part of sweeping changes the Australian government has spearheaded in recent years on online safety.

Supporters say the ban protects children from harmful content but critics say it is too blunt an instrument and efforts should focus on improving online safety.

The constitutional challenge in Australia's High Court was filed by the Digital Freedom Project a few weeks before the ban started on 10 December last year. The group is lead by New South Wales parliamentarian John Ruddick.

Two teens who originally spearheaded the case, Noah Jones and Macy Neyland, have since withdrawn as plaintiffs though Jones is still expected to attend Tuesday's hearing.

Speaking about the legal challenge last November, Jones told the BBC that there were bad things online but a blanket ban for under-16s was not the right answer.

"We shouldn't be using the resources and money of these social media platforms to try to avoid fines from our government," he said.

"They should be using this money and resources to try to get rid of the predators and harmful content out there."

Reddit also launched a High Court challenge to the ban, arguing the policy has serious implications for privacy and political rights.

Communications Minister Anika Wells last year said the government would not be "intimidated by legal threats."

"We will not be intimidated by big tech. On behalf of Australian parents, we will stand firm," she said last November.

Under the ban, ten platforms – Facebook, Instagram, TikTok, YouTube, Reddit, Snapchat, X, Kick, Threads and Twitch – must take "reasonable steps" to ensure no one under 16 years old can access its site.

Platforms risk fines of up to A$99m (US$70m, £52m) for serious or repeated breaches, but since the ban started, no company has been fined.

The eSafety Commissioner – the body tasked with enforcing the ban – has launched several investigations into alleged non-compliance by Facebook, Instagram, Snapchat, TikTok and YouTube.

WhatsApp and online gaming sites like Roblox and Discord were not included in the ban, nor were educational platforms like YouTube Kids and Google Classroom.

In the first few days of the ban, Meta – which owns three of the banned platforms – said it had closed about half a million accounts.

Some children said they were booted off their accounts in the days before and when the ban started – but many have said they were able to easily circumvent the age checks which included uploading credit card details, photo IDs or a selfie.