The world's biggest social media companies are not doing enough to keep children in Australia off their platforms, the country's internet regulator says, despite a law that came into effect late last year.

The legislation banned users under 16 from 10 platforms, but eSafety says it has "significant concerns" about the compliance of Facebook, Instagram, Snapchat, TikTok and YouTube.

Australia's ban - which is being closely watched by countries like the UK - was justified by campaigners and the government as necessary to protect children from harmful content and addictive algorithms.

Firms like Meta and Snap believe the approach is flawed, but say they're doing their best to comply.

In its first report since the ban took effect in December, the regulator said it had identified "a number of poor practices" across the five platforms.

These include:

• Giving children who had declared they were aged under 16 before the ban the chance to show that they were, in fact, over 16
• Enabling under-16s to repeatedly "attempt the same age assurance method"
• Insufficient measures to prevent new under-16s from creating accounts
• Not providing effective ways for parents and others to report under-16s who still have access to social media

Limited data has been released since the ban came into force. In January, the regulator said 4.7 million accounts had been restricted or removed in the first month since the law took effect on December 10.

"While social media platforms have taken some initial action, I am concerned through our compliance monitoring that some may not be doing enough to comply with Australian law," Australia's eSafety Commissioner Julie Inman Grant said.

The regulator – which had until now been monitoring the situation – says it will begin enforcing the restrictions and gathering evidence.

"The evidence must establish the platform has not taken reasonable steps to prevent children aged under 16 from having an account," Inman Grant said.

"That means more than simply demonstrating some children do still have accounts. Rather, the evidence must show the platform has not implemented appropriate systems and processes."

The BBC has contacted all of the social media companies for comment.

A spokesperson for Meta, which owns Facebook, Instagram, WhatsApp, Messenger, and Threads, said that the company is "committed to complying with Australia's social media ban". It also noted that accurate age determination is a "challenge for the whole industry" and argues that "robust age verification and parental approval" at the app store level is the most effective approach to protect young people.

Snap, which developed Snapchat, said it had locked 450,000 accounts and "continue to lock more every day".

While Australia's ban was introduced with great fanfare, it is widely acknowledged that many under-16s continue to use the 10 platforms covered by the law: Facebook, Instagram, Snapchat, Threads, TikTok, X, YouTube, Reddit, and streaming platforms Kick and Twitch.

When the BBC visited a school in Sydney last month, most students who used social media before the ban still had access. Some claimed they had not been asked to prove their age, while others said they had got around the age assurance methods.

One pupil claimed that, of 180 girls in her year group, she knew only three who had been booted off platforms.

Parents across Australia have widely supported the policy. For many, having the government on their side helps when they are at loggerheads with pre-teens desperate to get onto social media.

But there are plenty of critics, with technology experts and child wellbeing advocates saying children need to be educated on the potential harms on the platforms rather than banned from them.

And many question the ban's enforceability and say it unfairly excludes minority groups such as rural kids, disabled teenagers and those who identify as LGBTQ+ - all of whom are more likely to find their communities online.

On Tuesday, the eSafety commissioner said the reform was "unwinding 20 years of entrenched social media practices".

"Durable, generational change takes time - but these platforms have the capability to comply today," Inman Grant said.

"While the onus is on age-restricted platforms to take reasonable steps to keep children under 16 from having accounts, parents are proving pivotal partners in this cultural reset.

"We have heard from parents who have said the law is empowering them to say no to requests by their kids to have social media accounts.

"Any cultural change that pushes against the powerful interests and revenue potential of entrenched industry players - whether car manufacturers, Big Tobacco or Big Tech. Those players will push back but we continue to push ahead."