Platforms such as Facebook, Snapchat, TikTok and YouTube were already included in the ban – a world-first.

But the head of Australia’s eSafety commissioner Julie Inman Grant has written to 16 more companies to “self-assess” whether they fall under the ban’s remit.

The list also included Pinterest as well as Lego Play, streaming company Kick and gaming platform Steam.

Companies will need to make a case if they believe their platform should be exempt from the ban, the national broadcaster ABC said.

Inman Grant told the network that while some cases were “pretty clear”, the regulator would “give them the due diligence process”.

“We need to hear them all out,” she said.

The regulator said it will initially focus on platforms with the greatest number of users, where there are higher risks of harm.