The United Nations is to conduct an investigation into the controversial mass surveillance programmes carried out by the National Security Agency in the United States and its counterpart in Britain, GCHQ, it has emerged.

Ben Emmerson QC, the UN's special rapporteur on human rights and counter-terrorism, will probe the extent of the powers of the two intelligence agencies. This comes after former NSA contractor, Edward Snowden, blew the lid on secret surveillance on the public carried out by them, including tapping into phone calls and online activities. 

Emmerson said the investigation would particularly examine if the powers of GCHQ – which stands for Government Communications Headquarters – were greater than those that had been disclosed to the British parliament, and he will try to determine if there is sufficient control over the agency.

Public outrage was sparked on both sides of the Atlantic when newspapers published details of what GCHQ and the NSA had been clandestinely up to, after Snowden stole confidential files from his workplace and provided them to media organisations. The whistleblower fled the US and is currently living in Russia, where he has been granted temporary asylum. The US government has revoked his passport and wants him back home to face prosecution. 

Emmerson said the revelations from the Snowden leaks displayed "issues at the very apex of public interest concerns". He believes that instead of governments, such as the UK's, attacking news outlets that carried the reports, they should be supporting them as a cornerstone of democratic freedoms and in uncovering official wrongdoing for the benefit of the public.

The head of GCHQ, along with the bosses of fellow UK spy agencies MI5 and MI6, have said Snowden's leaking of covert surveillance operations was "a gift to terrorists" as the spying was designed to uncover any terror plots in the works. Emmerson said he was not convinced that the accusation is entirely accurate and his investigation will take testimony from the heads of all three organisations. 

Indeed, the special rapporteur said the Snowden revelations didn't appear to pose a risk to national security but instead benefited the public, because the agencies' actions had a direct impact on almost everybody. He is due to report his findings and recommendations to the UN general assembly next year.