SYDNEY, Aug 14 (Reuters) - Top social media platforms urged the Australian government not to place too much weight on early evidence showing most children still use their products despite a landmark under-16 ban, as lawmakers weigh tougher penalties and 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.

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 to use 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.

The eSafety commissioner is scheduled to testify at the inquiry later on Friday.