Major telecoms firms should make public whether they were obliged to give spies access to their networks, according to Labour MP Tom Watson.
"Let me be clear," Watson told MPs in a fiery debate that took place in Westminster Hall. "Telecoms companies have been illicitly aiding the security services to tap into data being processed by internet companies with whom they have a commercial relationship."
"These telecoms companies, who are the backbone of this wonderful thing called the internet, that has allowed two decades of free expression and creativity to explode into the lives of our citizens, have been operating in the shadows, to allow our security services to tap all of it."
The American NSA and the UK's GCHQ are accused of participating in a programme codenamed "MUSCULAR", which involved copying entire data flows that pass between the fibre-optic cables carrying information between data centres belonging to Silicon Valley tech giants.
The leaked documents even contained a jaunty post-it style sketch detailing the invasive and sprawling nature of the NSA's data collection. The sketch came replete with a "smiley" emoticon at the point where data was gathered by the three-letter agency.
A relatively obscure figure until recently, Tom Watson rose to prominence as a privacy activist when he questioned Rupert and James Murdoch, along with former News of the World editor Rebekah Brooks as a member of the Culture, Media and Sport Committee in July 2011.
Watson went on to say that "the security services have clearly made the trade-off that intelligence obtained is worth the invasion of privacy," while acknowledging that those agencies "are judged on the quality of the intelligence they obtain and little else."
However, large Internet firms are a different matter, he argued.
"I want to know if the telecoms companies have voluntarily entered into this agreement or if they have been obliged to under UK or USA law."
Watson added some comments on the validity of the actions of mega-leaker Edward Snowden, The Guardian, and its journalist Glenn Greenwald.
"We only know of the existence of the TEMPORA programme because of Edward Snowden and the Guardian newspaper," Watson added. "I think they have acted courageously in the public interest."
Google earlier released a statement in response to the MUSCULAR accusations:
"We have long been concerned about the possibility of this kind of snooping, which is why we have continued to extend encryption across more and more Google services and links."
The search giant went on to claim that "we do not provide any government, including the US government, with access to our systems."
Watson's calls were echoed by Conservative MP Dominic Raab, who argued that the legal justification for the GCHQ TEMPORA programme was "thin at best".
Concerning his own party leader, David Cameron, threatening the possibility of legal action against The Guardian for its role in publishing the leaks, Raab questioned:
"If national security were materially breached, why hasn't anyone at the Guardian been charged or even arrested since the search of their offices back in July?"
Lib Dem MP Julian Huppert joined the chorus, warning Britain was in danger of "sleepwalking" into a surveillance state.
Image: Flickr (Roger Lancefield)