Rod Sims, the chairman of the Australian Competition and Consumer Commission (ACCC), said in a speech on Tuesday that the watchdog is close to launching five cases against Google and Facebook for breaches of Australia's competition, consumer and privacy laws.
It comes after the ACCC conducted an inquiry into digital platforms, which found that there is an overarching need for reform to the sector.
"Facebook and Google either comply with our laws or they don't do business in Australia," Sims said.
"When you have these cases they are way more important than penalties because once you are found to have breached the law it is very difficult for the digital platforms to continue that behaviour," he added.
Sims could not go into details of the cases but the Australian Financial Review (AFR) reported on Wednesday that they are related to Facebook sharing user data with third parties and whether Google has unlawfully collated location and other data.
"Investigations start, they become in-depth then they become advanced and these are all very well advanced," he said.
"I know exactly where they are up to but until we institute (proceedings) we can't say anything," he added.
The ACCC's 600-page digital platform report was released in July, made 23 recommendations for stricter regulation and oversight.
Treasurer Josh Frydenberg in July described the findings as "groundbreaking", promising a full response from the government by the end of 2019.