Meta and TikTok allow children as young as 13 onto their platforms, though each cannot easily verify ages.
The 36 Months campaign co-led by media personality Michael "Wippa" Wipfli has also won support from comedian Hamish Blake, Hollywood actor Tahyna MacManus, business, academics and parents.
Even without platforms implementing a "very simple" technical method to verify age, enacting a legal minimum would empower young teens to stay away and parents to enforce bans, supporters say.
Wipfli denied mounting an attack on social media, saying Australia needed to acknowledge young children were more vulnerable to doom-scrolling and other key features of Instagram and TikTok.
"We need it (change) now - there are kids on the edge so we don't have time to waste," Wipfli said.
Eating disorder experts say teenagers need more time to develop without the influence of social media and want a ban for under-16s among other changes.
"The teenage years are the most prevalent age of onset for an eating disorder in Australia," the Australia and New Zealand Academy for Eating Disorders told a federal inquiry.
"Due to the loop of content reinforcing appearance ideals, control of eating etc. the algorithm can reinforce challenges related to the development of an eating disorder and treatment seeking and recovery."
Instagram's parent company says it has spent more than US$5 billion ($A7.5 billion) on safety and security in the past year alone.
Teens who search for content related to eating disorders or body image issues now see a pop-up with tips and an easy way to connect with support organisations such as the Butterfly Foundation.
"We have developed - and continue to review and update - our approach to eating disorder content in consultation with experts around the world," Meta has told a federal social media inquiry.
Age verification for the online purchase of alcohol has been trialled in NSW, with that state government flagging that it could inform similar pilots for social media.
A state-run summit in October is hoped to generate innovative solutions to the challenges of social media.
With AAP.
