Seven Internet service providers, including the UK-based GreenNet, have filed an official complaint at the investigatory powers tribunal in London charging Britain’s Government Communications Headquarters (GCHQ) with illegal surveillance.
The ISPs come from the US, UK Germany, South Korea, the Netherlands and Zimbabwe.
They have also joined forces with the anti-surveillance charity Privacy International, who unsuccessfully tried to take GCHQ to court last year over its use of spyware trained on UK internet users. The group accuses the agency of breaching UK laws, as well as the European Convention on Human Rights, which is designed to protect the privacy of all EU citizens.
"These widespread attacks on providers and collectives undermine the trust we all place on the internet and greatly endangers the world's most powerful tool for democracy and free expression." Eric King, deputy director of Privacy International, said in a statement.
The move follows last year’s revelations by ex-CIA whistleblower Edward Snowden, who exposed the global surveillance program PRISM deployed by the US National Security Agency.
"Snowden's revelations have exposed GCHQ's view that independent operators like GreenNet are legitimate targets for internet surveillance, so we could be unknowingly used to collect data on our users. We say this is unlawful and utterly unacceptable in a democracy," Cedric Knight, of GreenNet, told BBC News.
However, a GCHQ spokesman insisted the organization’s work operates “in accordance with a strict legal and policy framework which ensures that our activities are authorized, necessary and proportionate."
It is the first time GCHQ will have to face a private company in a courtroom.
The legal challenge comes following reports published this year in Der Spiegel earlier, which published reports claiming that Belgian telecoms employees were monitored and targeted by the British spy agency, based in Cheltenham in western England.
The reports also suggested that German internet exchange points were targeted, which allowed GCHQ to monitor internet traffic and infect users’ computers with viruses.