Facebook's oversight panel announced Thursday a probe of the company's system to reportedly exempt high-profile users from its own rules, accusing the embattled social media giant of a lack of transparency.

A series of damning Wall Street Journal stories driven by a whistleblower's leaks have drawn outrage and fresh lawmaker scrutiny of Facebook's impact on mental health but also how it treats celebrities.

The so-called "cross-check" or "XCheck" system shields millions of elite users from rules that Facebook claims to apply equally at the social media giant, according to Journal reports citing internal documents.

The network's semi-independent oversight board said in a blog post that it "has accepted a request from Facebook... to review the company's cross-check system and make recommendations on how it can be changed."

Facebook has faced a storm of criticism over the past month after former employee Frances Haugen leaked internal studies showing the company knew of potential harm stoked by its sites, prompting US lawmakers' to renew a push for regulation.

The Facebook-funded oversight board, composed of experts with the final say on what is removed or allowed to stay on the platform, also criticized the company for failing to be "fully forthcoming".

"On some occasions, Facebook failed to provide relevant information to the Board, while in other instances, the information it did provide was incomplete," the panel said, referring to queries about the cross-check system.

Specifically it cited the platform's ban on former US president Donald Trump, which it reviewed and ultimately upheld but with sometimes incomplete information from Facebook.

Facebook has been hit with fresh criticism for its handling of a key program
Facebook has been hit with fresh criticism for its handling of a key program AFP / MANDEL NGAN

Facebook subsequently set Trump's ban at two years, saying he deserved the maximum punishment for violating platform rules over a deadly attack by his supporters on the US Capitol.

"The credibility of the oversight board, our working relationship with Facebook, and our ability to render sound judgments on cases all depend on being able to trust that information provided to us by Facebook is accurate, comprehensive, and paints a full picture of the topic at hand," the board wrote.

It added that of the 156 questions sent to Facebook about decisions published through the end of June, the company answered 130, partially answered 12 and declined to answer 14.

Facebook, in a statement, pledged to be clearer in its replies to the panel's queries.

"We believe the board's work has been impactful, which is why we asked the board for input into our cross-check system, and we will strive to be clearer in our explanations to them going forward," the statement said.

The tech giant has pushed back fiercely against the latest criticism, saying journalists have selectively chosen parts of its internal research in order to cast the company's work in a negative light.

The Journal cited examples of posts from high-profile people, including one from soccer star Neymar showing nude images of a woman who accused him of rape and that Facebook subsequently removed.

Famous users' posts are drivers of engagement on the platform, so keeping celebrities on Facebook is important for a company interested in continuous growth.

An activist group calling itself The Real Facebook Oversight Board attacked the panel's work and even its reason for existing.

"The Oversight Board always was a PR stunt by Facebook to paper over and deflect from the company's own failure to keep hate, racism and disinformation off its platforms," it said in a statement.