A class-action civil suit against Facebook’s data collection practices has attracted over 20,000 co-complainants just five days after its launch.

The class-action suit, dubbed a "David and Goliath" battle against the US social network, was launched by Austrian privacy campaigner Max Schrems and uses Facebook's own network to collect applications for the lawsuit against it.

The campaigner said yesterday the level of interest in the campaign - fbclaim.com - exceeded even his most optimistic expectations. Applications will close at 25,000 participants, to enable his legal time process the applications for inclusion in the civil case before a Vienna court.

“This number of participants is a really good basis to not just complain about data protection but to do something about it,” said Mr Schrems. “If successful the result will be an improvement for all users.”

Over half of the applicants come from three countries - Germany, Austria and the Netherlands - with other top 10 countries including, in descending order, Finland, Croatia, Britain, Belgium, France, Serbia and Poland.

The civil suit in Vienna will run in parallel to another case brought by Mr Schrems against the Irish Data Protection Commission (DPC), challenging its decision not to investigate allegations that Facebook shared European user data with the NSA via its Prism programme. That case was heard before the High Court in Dublin before being passed on for legal clarification to the European Court of Justice (ECJ).

The new civil suit is open to all Facebook users outside of the US and Canada as they have a contract with Facebook International, based in Dublin.

Under Austrian law, the users have to actively agree to sign up to the Schrems civil suit. To do this, he has set up an app via fbclaim.com which uses Facebook’s own network to collate the claims.

The case claims Facebook International uses US data protection guidelines that are invalid under EU law. It claims the company collects data without securing adequate user consent and, in breach of EU law, passes on European user data to the NSA’s Prism surveillance programme. In addition the class action suit challenges Facebook’s practice of tracking users outside of its own network, through the “Like” button on websites. The case challenges what it calls Facebook’s “Big Data” practices, by which it says the company merges user data from various sources without explicit user consent. The case takes issue with Facebook’s “Graph Search” function which, Schrems claims, saw the company alter user terms of service to obtain user consent. Finally, the Austrian case claims Facebook illegally passes on user data to third parties.

The civil case has been filed in Vienna and will be heard under Austrian law. However, the Austrian campaigners have decided to use Californian law for compensation purposes, an option they say is available to them thanks to Facebook International’s hybrid legal status.

“This is very helpful for pushing through our rights,” said Mr Schrems. “But the compensation claim has been kept deliberately low - €500 per user -- because, for us, it is about proper data protection. But if a few thousand people participate, we will reach an amount that Facebook will feel.”

This class-action civil suit follows Mr Schrems’s decision to withdraw his original Facebook complaint to the DPC, arguing the social network’s data collection policies breached EU law.

Mr Schrems said he withdrew h is Irish case after three years because he was not convinced there was any interest by the Irish authorities to take legal action against Facebook.