A lawyer planning to sue Facebook in a class action over online privacy has limited the number of plaintiffs to 25,000 after he was overwhelmed with support.

Campaigner and lawyer Max Schrems has accused Facebook Ireland – the Irish subsidiary of the website - of breaching European data laws, and violating users’ rights by tracking internet activity on external sites, including the use of “like” buttons.

The lawsuit, organised via Mr Schrem's Europe-V-Facebook.org, also questions how Facebook analyses users through what it calls “big data” systems. Mr Schrems claims the company supports the US secret service’s Prism surveillance exposed by whistleblower Edward Snowden.

The law suit, which is being launched against the New York-listed 1.3 billion user-strong social media giant, could be the largest class and privacy action ever taken.

Mr Schrems is restricting the case to 25,000 people so each Facebook account can be verified. But he will continue to register the information of users who wish to join the action, who will be prioritised if the claim is expanded.

Up to 7,000 users a day from more than 100 countries have registered their support for Schrems's David v Goliath legal challenge, which will take place in Austrian courts.

10 facts you didn’t know about Facebook Show all 10 1 /10 10 facts you didn’t know about Facebook 10 facts you didn’t know about Facebook Around 350 million photos are uploaded to Facebook every day, with the site estimating in September last year that users had so far put up more than 250 billion images. That’s 4,000 photos uploaded every second and around 4 per cent of all photos ever taken, according to a study by Nokia. REUTERS/Shannon Stapleton 10 facts you didn’t know about Facebook Facebook’s logo is blue because Mark Zuckerberg is red-green colour blind. “Blue is the richest color for me. I can see all of blue," said Zuckerberg in an interview with the New Yorker. The colour is so popular that Facebook’s campus store even sells nail polish in the exact shade named ‘social butterfly blue’. REUTERS/Robert Galbraith 10 facts you didn’t know about Facebook Zuckerberg's famously low-key wardrobe (either a grey t-shirt or a hoodie) is so that the CEO saves time deciding what to wear each day. However, Zuckerberg is known to dress up when the occasion demands it. For a 2011 event with Barack Obama he showed up in a suit, with the president introducing himself by saying: “I’m Barack Obama and I’m the guy who got Mark to wear a jacket and tie.” REUTERS/Brian Snyder 10 facts you didn’t know about Facebook In July 2006 Zuckerberg turned down a $1 billion offer for the site from Yahoo. He was 22 years old at the time and owned 25 per cent of the company. Zuckerberg reportedly turned it down by saying “I don't know what I could do with the money. I'd just start another social networking site. I kind of like the one I already have.” He definitely made the right choice: Facebook is now valued at $135 billion. 10 facts you didn’t know about Facebook A YouGov poll claimed that three-quarter of UK Facebook users' photos showed someone drinking or inebriated. However, the poll did ask users to estimate the number of boozy snaps themselves, and like all things on Facebook, there might have been an element of exaggeration involved. REUTERS/Robert Galbraith 10 facts you didn’t know about Facebook Facebook operates a bounty hunter program – for bugs. Like many other big technology companies Facebook offers cash rewards to security researchers who point out flaws in the site’s code. The minimum payout is $500 and the largest prize to date has been $33,500. REUTERS/Robert Galbraith 10 facts you didn’t know about Facebook More than a third of divorce filings in 2011 referenced Facebook, said a survey from UK-based legal firm Divorce Online. The exact figures may be an estimate, but with just under 8 trillion Facebook messages sent in 2013 it’s certain that a substantial body of evidence is to be found on the social network. 10 facts you didn’t know about Facebook Zuckerberg isn’t much of a Twitter fan. Despite having nearly three hundred thousand followers on the service he’s only tweeted 19 times - once in 2012 and the rest in 2009. Although Facebook dwarfs twitter in terms of active users (1 billion compared with 200 million by some accounts) the micro-blogging site handles breaking news better. Facebook has introduced trending topics and hashtags to counter this. 10 facts you didn’t know about Facebook Following the financial crisis of 2008 and 2009 Iceland decided to rewrite their constitution using Facebook to solicit suggestions from citizens. Unfortunately, despite this forward thinking approach, the document was killed by politicians in mid-2013 for various (mostly technical) reasons. 10 facts you didn’t know about Facebook You can browse Facebook upside down. Facebook currently supports more than 70 different languages – including English (Pirate) and English (Upside Down). Check the bottom of the column on the right of your newsfeed and click your current language to change!

Mr Schrems hopes to claim damages of €500 euros (£397) per supporter.

Last Friday, the number of people signing up peaked as a new user joined every six seconds.

Max Schrems begins petition against Facebook

“We have hoped for large support, but the number of participants in such a short time exceeded my most optimistic expectations,” he said.

Most plaintiffs are from Germany, where 5,287 Facebook users have signed up, while 944 users are based in the UK and only 162 from Ireland - as of 9am on Wednesday.

Support for the campaign is also strong in Austria, with 3,712 users, the Netherlands, with 2,438, Finland, with 1,179, and Croatia with 1,106.

Facebook has several weeks to respond to Mr Schrems's claims.

An earlier landmark battle launched in Ireland to find out what Facebook tells US spy chiefs was referred to the European Court of Justice by a judge in Dublin last month.