The inquiry into the federal government's Digital Duty of Care bill on Monday heard testimonies from parents, experts and stakeholder organisations.
Under the draft legislation, online services and platforms would be required to adhere to a set of safety standards, putting the onus of protection and harm reduction on technology companies.
Representatives from Meta, Google, TikTok Australia and Snap Inc agreed with the bill in principle to protect Australians from online harm.
But they called for significant changes to address concerns over vague provisions, broad enforcement powers and a rushed consultation process.
"I'd just encourage you, as a committee and the parliament more broadly, to fully understand what that type of change would mean," TikTok's Jessika Lofstedt said.
"Not just for platforms like us, but more importantly for websites, for e-commerce platforms, for AI companions, all the way through to the gaming platforms."
Committee deputy chair Sarah Hanson-Young asked whether the tech representatives believed Australians should be able to seek justice or compensation if they had suffered harm from online platforms.
While Ms Lofstedt defended the existing Online Safety Act as a strong, well-established, and robust framework offering various paths for recourse, Senator Hanson-Young countered these measures failed to provide direct avenues for victims.
The Greens senator also questioned their views on tying penalties to global revenue or profits.
Meta, which owns Facebook and Instagram, in 2026 paid two multibillion-settlements and fines in the United States around child safety and platform addiction, and user data privacy.
It received its largest ever fine in October of $US25 billion ($A36 billion) after a jury found the company had lied about how it handled users' personal data.
"Our primary focus is on compliance and avoiding having to discuss penalties," Meta's Mia Garlick told the inquiry.
"We have a commercial interest to make sure that people have a positive use on our services."
The representatives provided little information regarding fines paid in Australia, with some questions taken on notice.
They were also challenged by independent senator David Pocock over claims self-harm content was appearing on platforms.
"How can you seriously try and tell the committee that you don't have that content on your platform when you clearly do?" Senator Pocock said.
Ms Lofstedt rejected this assertion, citing TikTok's strict community guidelines and inviting the committee to provide specific examples for investigation.
Chanel Contos, founder and chief executive of sexual violence prevention organisation Teach Us Consent, said she supported the bill, citing an "urgent need to regulate big tech and make online spaces safer".
She called for amendments that would see fines tied to a percentage of a company's global revenue, and a private right of action that would give individuals the right to sue tech companies and seek compensation.
Heads Up Alliance founder Dany Elachi said while he strongly supported the online protection of young people, he rejected the government's "nebulous" bill, accusing it of being marked by the "fingerprints of illiberalism".
He said the bill tied child protection with adults' online free speech, which ought to be two separate issues and not a two-for-one deal.
Communications Minister Anika Wells has defended the government's work on the bill as courageous, saying it would create a better environment for the next generation of Australian children.
"It's about embedding some basic safety standards and saying to big tech: if you build it, you are responsible for its risks," she told ABC News.
Conservative politicians and groups have described the plan as censorship and raised concerns about data collection.
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