Australia's Privacy Commissioner has launched a formal investigation into social media giant Facebook, in the wake of the Cambridge Analytica scandal.

Key points: Facebook estimates 311,000 Australians are among the 87 million users worldwide whose data may have been compromised

Facebook estimates 311,000 Australians are among the 87 million users worldwide whose data may have been compromised It says it does not know "precisely what data the app shared" with data analysis firm Cambridge Analytica

It says it does not know "precisely what data the app shared" with data analysis firm Cambridge Analytica Acting Information and Privacy Commissioner Angelene Falk says the Australian investigation will coordinate with international authorities

Facebook has revealed more than 300,000 Australians may have had their private data used without their knowledge.

Acting Information and Privacy Commissioner Angelene Falk said the investigation would determine whether Facebook had breached Australia's Privacy Act.

Under a recently introduced Notifiable Data Breaches scheme, the commissioner has the power to issue fines of up to $2.1 million to organisations that fail to comply with the act.

"Given the global nature of this matter, the [Office of the Australian Information Commissioner] will confer with regulatory authorities internationally," Ms Falk said.

The social media giant has revealed up to 87 million users may have been affected worldwide.

The majority of those users are in the US, where the Trump-affiliated, data-analysis firm Cambridge Analytica has been accused of tapping profiles without users' permission in order to influence elections, including during the 2016 presidential campaign.

Facebook's graph of people affected by the Cambridge Analytica scandal. ( Supplied: Facebook )

Facebook said it did not know precisely what information was shared with Cambridge Analytica, but pledged to restrict access from apps to personal profiles and to notify users who may have been affected.

Cambridge Analytica denied wrongdoing, but was suspended from Facebook over the allegations and had its London offices raided.

"All organisations that are covered by the Privacy Act have obligations in relation to the personal information that they hold," Ms Falk said.

"This includes taking reasonable steps to ensure that personal information is held securely, and ensuring that customers are adequately notified about the collection and handling of their personal information."

The Acting Commissioner argued the incident should serve as a warning to protect private data.

The Federal Government declined to comment on the investigation, saying it would await the commissioner's findings.