BSS/AFP) - Online discussion site Reddit launched a legal challenge Friday to Australia`s social media ban for under-16s, just days after the landmark law came into effect.

This week, the country became the first to ban young teen accounts from a raft of popular apps and sites including TikTok, YouTube and Instagram.

Tech companies that fail to purge Australia-based users younger than 16 now face fines of Aus$49.5 million (US$33 million).

Court filings by US-based Reddit challenged the validity of the law that "infringes the implied freedom of political communication", calling for a review by Australia`s High Court.

The filing also argued that the company should be exempt from the government`s list of banned platforms, on the grounds that it is an online discussion forum aimed at adults.

"Unlike other platforms included under this law, the vast majority of Redditors are adults, we don`t market or target advertising to children under 18," a Reddit statement said.

"Simply put, users under 16 are not a substantial market segment for Reddit and we don`t intend them to be."

Pointing to the site`s age rating of "17+" on the Apple App Store, Reddit said the best way to verify age was at the app store level rather than requiring each platform to carry out checks.

A spokesperson said there were serious privacy concerns associated with platforms verifying age, with the collection of personal data creating a risk of leaks or hacks.

The government was also inconsistent in selecting which platforms should be banned, the spokesperson argued, with some apps with large under-16 user groups exempt.

Those include Roblox, Pinterest and WhatsApp, but the government has stressed that the list remains under review.

- `Missing the mark` -

Reddit criticised the law as "missing the mark on protecting young people online".

"While we will comply with this law, we have a responsibility to share our perspective and see that it is reviewed by the courts," Reddit said.

The sprawling forum site made up of thousands of niche communities had previously warned on the eve of the December 10 ban that the government`s move was "legally erroneous".

It is not the only tech firm to condemn the ban -- Meta, the parent company of Facebook and Instagram, also raised concerns that teens could flock to darker, less regulated corners of the internet seeking connection with peers.

An Australian government spokesperson said Friday authorities were "on the side of Australian parents and kids, not platforms".

"We will stand firm to protect young Australians from experiencing harm on social media."

Reddit`s case is separate from one filed by an internet rights group last month, which is also seeking to overturn the law on the grounds it is an "unfair" assault on freedom of speech.

Australia`s ban is being closely watched worldwide, with New Zealand and Malaysia mulling similar restrictions.

The government concedes the ban will be far from perfect at the outset and canny teenagers will find ways to slip through the cracks.

But authorities say unprecedented measures are needed to protect children from "predatory algorithms" filling phone screens with bullying, sex and violence.