Belgium's privacy watchdog has accused Facebook of trampling on European privacy laws and dodging questions from national regulators.
The Privacy Protection Commission (CPVP/CBPL), which is working with German, Dutch, French and Spanish counterparts, launched the blistering attack after trying to find out more about the U.S. social media giant's practices.
It urged Internet users to install privacy software to shield themselves from Facebook's tracking systems, whether they have an account with the social network or not.
The show of strength from the Belgian regulator, which does not have the power to levy fines, highlights a growing willingness across the 28-member bloc to demand that big U.S. tech companies abide by European laws.
"Facebook tramples on European and Belgian privacy laws", the Commission said after publishing a report analysing changes that the company made to its privacy policies in January.
It said in a statement that Facebook had refused to recognise Belgian and other EU national jurisdictions, insisting it was subject only to the law in Ireland, the site of its European headquarters.

"Facebook has shown itself particularly miserly in giving precise answers," the watchdog said, adding that the results of the study by a group of researchers were "disconcerting".