Data-protection authorities have been urged to tell Facebook to halt what consumer organisations believe is a privacy- intrusive plan to track users' internet browsing activity.

A group representing European consumer organisations has written to the Irish Data Protection Commissioner and the US Federal Trade Commission asking them to investigate a recently announced change in Facebook's business practices.

The Transatlantic Consumer Dialogue (TACD), notes that Facebook announced in June that it planned to collect more data so as to serve users targeted advertising. Facebook already uses cookies and pieces of code known as "pixel tags" to track browsing activity on its own website and on Facebook apps.

However the consumer group said the proposed change would mean those pieces of code would also track users’ browsing activity on any other website that included “a few lines of Facebook code”.

Facebook says its “partners” may use such pixel tags on their sites so that it may later serve them a relevant ad on Facebook.

“TACD is calling on regulators to require Facebook to suspend this change in policy and determine whether it complies with current US and EU law,” the organisation said.

It believes Facebook’s proposed “data collection expansion” directly contradicts previous statements about how it would use its customers’ data.

“Contrary to its prior representations . . . the company will now routinely monitor the web-browsing activities of its users and exploit that information for advertising purposes.”

In a note on its blog, Facebook said: “When we ask people about our ads, one of the top things they tell us is that they want to see ads that are more relevant to their interests. If you don’t want us to use the websites and apps you use to show you more relevant ads, we won’t.”