The legal action follows Instagram users reporting in July that they had noticed the FaceTime symbol, which indicates that an iPhone camera is on, was showing up when they scrolled their feeds.

At the time, Facebook denied spying accusations and blamed the issue on a bug, which, it said, triggered false notifications that Instagram was accessing cameras.

However, now a lawsuit, filed in a federal court in San Francisco on Thursday, insists that the tech giant was doing it on purpose.

The Instagram app was activating smartphone cameras without notifying the owners of the phones in order to gather “lucrative and valuable data that it would not otherwise have access to,” plaintiff Brittany Conditi from New Jersey claims in the suit.

This “extremely private and intimate” personal information, “including in the privacy of [the users’] own homes,” allowed Facebook, which makes most of its income from selling ads, to gain “valuable insights and market research,” according to the complaint.

Facebook is “able to see in-real time how users respond to advertisements on Instagram, providing extremely valuable information to its advertisers,” she said.

The company already faced similar accusations in November last year when users said the Facebook app was accessing cameras on their iPhones without their permission.

In August, another lawsuit was filed against Facebook, accusing Instagram of employing facial-recognition technology to collect people’s biometric data. The tech giant insisted that its app didn’t use facial recognition technology at all.