Academic researchers said that the report showed that the company was breaking European law with its tracking policies. The law requires that users are told if their computers are receiving cookies except for specific circumstances.

Facebook’s tracking — which it does so that it can tailor advertising — involves putting cookies or small pieces of software on users’ computers, so that they can then be followed around the internet. Such technology is used by almost every website, but European law requires that users are told if they are being given cookies or being tracked. Companies don’t have to tell users if the cookies are required to connect to a service or if they are needed to give the user information that they have specifically requested.

But Facebook’s tracking policy allows it to track users if they have simply been to a page on the company’s domain, even if they weren’t logged in. That includes pages for brands or events, which users can see whether or not they have an account.

Facebook disputes the accusations of the report, it told The Independent.

“This report contains factual inaccuracies,” a Facebook spokesperson said. “The authors have never contacted us, nor sought to clarify any assumptions upon which their report is based. Neither did they invite our comment on the report before making it public.

“We have explained in detail the inaccuracies in the earlier draft report (after it was published) directly to the Belgian DPA, who we understand commissioned it, and have offered to meet with them to explain why it is incorrect, but they have declined to meet or engage with us. However, we remain willing to engage with them and hope they will be prepared to update their work in due course”.

The report does not have any legal standing, and was written by independent academics.

With respect to its European data, Facebook is regulated by the Irish Data Protection Commissioner, who checks that Facebook is acting within the EU’s Data Protection Directive. As part of that regulation, Facebook is regularly audited.

Facebook has a page on its site that gives users’ information about cookies and .... The company makes clear that cookies are used for the purposes of advertising and other functions, and that users can opt out of such tracking if they wish to.