Top social media platforms urged the Australian government not to place too much weight on early evidence showing that most children still use their products despite a landmark under-16 ban, as lawmakers consider tougher penalties and greater investigative powers for regulators.

Local heads of YouTube owner Google, Facebook and Instagram owner Meta, Snapchat and TikTok fronted a Senate inquiry ​as lawmakers pressed them on multiple studies, including from Australia's internet regulator, showing some 80% of minors were still ​on social media months after the ban took effect in December.

The hearing showed a persisting divide ⁠between lawmakers and big tech over whether the ban is working at a time when the eSafety Commissioner is considering ​legal action against some platforms, accusing them of deliberately slow-walking compliance to discourage other jurisdictions from copying it.

Commissioner Julie Inman Grant ​told the inquiry the March data suggested platforms were "failing to prevent the creation and recreation of accounts" but insisted the ban was showing early signs of working, citing a modest decline in numbers of underage accounts.

"We are seeing change but we need to give it time," Inman ​Grant said.

"Once that active enforcement starts, that's when the behaviour starts to change."

The inquiry is examining amendments that would double maximum ​penalties to A$99 million ($64 million) and expand the commissioner's powers to compel information and documents from platforms and their third-party age assurance providers ‌during investigations.

"It is a point in time, it's very early on, and we caution against over-reliance on that," YouTube's head of government relations Rachel Lord told the inquiry, noting the government's latest published compliance data was from March.

Age assurance technology had largely been built around a cut-off of 18, which many jurisdictions consider the transition from childhood to adulthood, and "the technologies that we are ​using to detect users at ​the 16 age boundary are ⁠evolving", Lord added.

Meta's Australia head of public policy Mia Garlick said the data on which the research was based may not reflect whether underage users had an account, even if they ​claimed to use a platform.

"There can be differences in terms of people accessing versus having ​an account," she ⁠told the inquiry.

"Sometimes survey data is challenging in terms of stated versus revealed."

Meta released figures a day earlier showing it had deactivated 756,000 Instagram and Facebook accounts suspected of belonging to underage users, up from about 500,000 in March. YouTube's Lord said Google has stopped about 740,000 holders of Google accounts from using their accounts on YouTube.

TikTok's Australian head of public policy, Jessica Loftstedt, said the company's compliance efforts were an "iterative process". The company had taken down 550,000 accounts when the law took effect ​and had since been removing about 24,000 a month.