Facebook CEO Mark Zuckerberg has begun a two-day congressional inquisition by apologising for the social media giant’s worldwide privacy breach.

But, Mark Zuckerberg is defending the amount of time it took to notify users about the Cambridge Analytica data scandal.

Facebook admits 87 million users, including about 300,000 in Australia, are caught up in the breach.

The company purchased the data from an app, linked to Facebook accounts.

While testifying before US Congress, Zuckerberg insists he did take steps to rectify the situation, but admits he made mistakes.

“We took down the app and we demanded that both the app developer and Cambridge Analytica delete and stop using any data that they had.

“They told us that they did this.

“In retrospect, it was a clearly a mistake to believe them and we should have followed up and done a full audit then and that is not a mistake that we will make.”

Ross Greenwood isn’t buying it.

“Give me a break.

“They’re allowing fake news to proliferate. They’re not trying to stop it at all,” he says.

CSIRO research leader Professor Dali Kassfar tells Ross users have effectively been paying to use the platform.

“In one way or another, we have been paying.

“The currency is our data… Facebook has never been free.

“If you’re not paying for the product, then probably you are the product.”

Listen to the full interview below