Facebook could face millions in fines with Australia's privacy watchdog taking the social media giant to court.
The Australian Information Commissioner lodged court documents on Monday alleging users unwittingly had their personal data used for political purposes.
The commissioner is alleging in Federal Court that Facebook allowed Australian users' personal data to be sold for political profiling by a third-party app.
That data was sent to now-defunct British consultants Cambridge Analytica, which used Facebook information in 2015 without permission to profile American voters.
Commissioner Angelene Falk claims 311,127 Australians had their Facebook data sold and used for purposes that include political profiling.
"Users were unable to exercise reasonable choice and control about how their personal information was disclosed," she said.
"Facebook's default settings facilitated the disclosure of personal information, including sensitive information, at the expense of privacy."
Users of the app This Is Your Digital Life - and even their friends who did not install the app - had their data sold on.
Court documents lodged by the watchdog say most of the people who had their data sold didn't even install the app.
The producers of the app sold that data to Cambridge Analytica, it's alleged.
"As a result, the affected Australian individuals' personal information was exposed to the risk of disclosure, monetisation and use for political profiling purposes," court documents say.
Facebook paid a record $US5 billion fine to resolve a US government probe into the Cambridge Analytica scandal.
Australia's Federal Court could whack Facebook with a $1.7 million fine for each privacy offence, with court documents saying each individual disclosure of information was a breach of the Privacy Act.
