Three British campaign groups have launched a legal challenge against the actions of GCHQ with the European Court of Human Rights.
Big Brother Watch, the Open Rights Group and English PEN, together with German internet activist Constanze Kurz, are to file papers against the UK government, alleging it has illegally intruded on the privacy of millions of British and European citizens.
The groups alleges that by collecting vast amounts of data leaving or entering the UK, including the content of emails and social media messages, GCHQ has acted illegally.
The move comes after months of revelations by Edward Snowden about the extent to which the NSA and GCHQ have developed industrial-scale capabilities to monitor global internet traffic.
The applicants specifically reference the Prism and Tempora programmes, codenames for previously secret surveillance operations which allow the authorities to hoover up vast amounts of web traffic with Tempora giving the UK authorities the ability to tap directly into vast amounts of data carried on undersea cables.
Reports suggest that GCHQ has the capacity to collect more than 21 petabytes of data a day, equivalent to sending all the information in all the books in the British Library 192 times every 24 hours.
Daniel Carey, solicitor with Deighton Pierce Glynn, which is taking the case, told the Guardian:
"We are asking the court to declare that unrestrained surveillance of much of Europe's internet communications by the UK government, and the outdated regulatory system that has permitted this, breach our rights to privacy."
Nick Pickles, director of Big Brother Watch, one of the groups bringing the legal challenge, said the laws governming this area were outmoded:
"The laws governing how internet data is accessed were written when barely anyone had broadband access and were intended to cover old-fashioned copper telephone lines. Parliament did not envisage or intend those laws to permit scooping up details of every communication we send, including content, so it's absolutely right that GCHQ is held accountable in the courts for its actions."
The Tempora programme is given legal authority by the Regulation of Investigatory Powers Act (Ripa) which has been in force since 2000 and oversees all collection of data by the UK government.