Washington (AFP) - A consortium of US states announced a joint probe Thursday of Instagram's parent company Meta for promoting the app to children despite allegedly knowing its potential for harm, in fresh regulatory trouble for the scandal-hit network.

The social media giant is battling one of its most serious reputational crises yet after a whistleblower leaked reams of internal documents showing executives knew of their sites' risks for teens' well-being, prompting a renewed US push for regulation.

"Facebook, now Meta, has failed to protect young people on its platforms and instead chose to ignore or, in some cases, double down on known manipulations that pose a real threat to physical and mental health -- exploiting children in the interest of profit," Massachusetts Attorney General Maura Healey said in a statement.

The consortium of attorneys general -- states' top law enforcers and legal advisors -- includes New York, Colorado, California, Florida, Kentucky, Nebraska, New Jersey, Tennessee, and Vermont.

The investigation targets, among other things, Meta's techniques for increasing the frequency and duration of engagement by young users and the resulting harms, said California Attorney General Rob Bonta.

It comes after "reports revealing that Meta's own internal research shows that using Instagram is associated with increased risks of physical and mental health harms on young people, including depression, eating disorders, and even suicide," Bonta's statement said.

Whistleblower crisis

Meta fired back at the probe, saying the allegations were untrue and that it has worked to protect youth online.

"These accusations are false and demonstrate a deep misunderstanding of the facts," the firm's statement said.

"We continue to build new features to help people who might be dealing with negative social comparisons or body image issues, including our new 'Take a Break' feature and ways to nudge them towards other types of content," it added. 

The recent leak of Facebook documents have underpinned a deluge of damning stories, including blaming CEO Mark Zuckerberg for his platform bending to state censors in Vietnam and highlighting how the site has stoked anger in the name of keeping users engaged.

The tech giant changed its parent company name to "Meta" in October as it sought to move past the wave of scandals, and focus attention on its virtual reality vision for the future.

The documents were given to lawmakers, a consortium of journalists and US regulators by former Facebook employee Frances Haugen, who has become a figurehead of criticism of the leading social media platform.

Haugen told AFP in a wide-ranging interview that she believes young people have more reason than anyone else to pressure social media companies to do better.

"I want to start a youth movement," she said, adding that youngsters who have grown up online should not feel so "powerless" over the social networks enmeshed in their lives.

Haugen has spent nearly two months in the spotlight over her claims that Facebook has consistently prioritized profits over people's safety.

As the scathing media reports were published, Facebook noted in a regulatory filing that from September "it became subject to government investigations and requests" relating to the leaked files.