UK's spy agencies gained secret access to fibre-optic cables carrying global communications and gathered data larger than the US, a media report today said, quoting documents leaked by American whistleblower Edward Snowden.
The Guardian newspaper said the revelations were based on leaked documents from the GCHQ - the UK's electronic eavesdropping agency.
The information, including phone calls, Facebook posts, emails, Internet histories, was stored for up to 30 days to be sifted and analysed, the paper alleged.
The GCHQ has started processing vast amounts of personal information and is sharing it with its US partner the National Security Agency (NSA), it said.
GCHQ declined to comment on the claims but said its compliance with the law was "scrupulous".
The documents were reportedly released by whistleblower Snowden, a former IT contractor at GCHQ's US counterpart, the National Security Agency (NSA), who is believed to be in hiding in Hong Kong following a series of shocking disclosures about US intelligence operations.
It is reported that US authorities have charged 30-year-old Snowden with espionage and theft.
It's not just a US problem. The UK has a huge dog in this fight," Snowden told the Guardian.
"They [GCHQ] are worse than the US."
According to the Guardian, the GCHQ (Government Communications Headquarters) operation codenamed Tempora has been running for 18 months and was able to boast a larger collection of data than the US, tapping into 200 fibre-optic cables to give it the ability to monitor up to 600 million communications every day.
The two main components of GCHQ's surveillance programme are called "Mastering the Internet" and "Global Telecoms Exploitation", the newspaper said, adding that the operations were all being carried out "without any form of public acknowledgement or debate".
Shami Chakrabarti, director of human rights group Liberty, said she was shocked by the report and accused GCHQ of allowing itself a "very generous interpretation of the law".
"They are exploiting the fact that the Internet is so international in nature.
"And I'm pretty sad in a democracy when all that appears to be holding back the secret state is its physical and technological capability and not its ethics or a tight interpretation and application of the law," she told BBC Radio.
