Two Facebook users are suing the social media website claiming it sells information from users’ private messages to advertising companies without consent.

In the lawsuit filed in the Northern District of California court in the US, Americans Matthew Campbell and Michael Hurley accuse Facebook of scanning private messages that contain links to other websites.

Court papers said Facebook then shared that information with third parties such as advertisers and marketers.

If true that would violate the US government’s Electronic Communications Privacy Act and California state privacy laws

The lawsuit is based partly on a report by a Swiss security firm High-Tech Bridge.

HTB tested user privacy on 50 social networks, Web services and free email systems by sending messages with a different secret website link in each. It then monitored which of the services clicked on those links and reported that Facebook was one of those that did.

Campbell and Hurley want the court to ban Facebook from scanning messages as well as financial compensation for damages.

Facebook said the allegations were without merit and promised a vigorous defence if the matter comes to court.