Critics react angrily to revelation that GCHQ intercepted and stored millions of images of people not suspected of wrongdoing

Politicians and human rights groups have reacted angrily to revelations that Britain's spy agency intercepted and stored webcam images of millions of people not suspected of any wrongdoing with the aid of its US counterpart.

GCHQ files dating between 2008 and 2010 reveal that a surveillance program codenamed Optic Nerve collected images of Yahoo webcam chats in bulk and saved them to agency databases, regardless of whether individual users were an intelligence target or not.

In one six-month period in 2008 alone, the agency collected webcam images, including substantial quantities of sexually explicit material, from more than 1.8 million Yahoo user accounts globally.

The Tory MP David Davis said:

"We now know that millions of Yahoo account holders were filmed without their knowledge through their webcams, the images of which were subsequently stored by GCHQ and the NSA. This is, frankly, creepy."

Davis, said it was perfectly proper for the intelligence agencies to use any and all means to target those suspected of terrorism, kidnapping and other serious crimes, but that the indiscriminate nature of the programme was alarming.

"It is entirely improper to extend such intrusive surveillance on a blanket scale to ordinary citizens," he said.

The Liberal Democrat MP Julian Huppert said he was "absolutely shocked" at the revelation. "This seems like a very clear invasion of privacy, and I simply can not see what the justification is," he said.

The Optic Nerve documents were provided by the NSA whistleblower Edward Snowden. They show that the programme began as a prototype in 2008 and was still active in 2012.

They chronicle GCHQ's sustained efforts to keep the large store of sexually explicit material Optic Nerve collected away from the eyes of its staff, though there is little discussion about the privacy implications of storing it in the first place.

The system, eerily reminiscent of the telescreens evoked in George Orwell's 1984, was used for experiments in automated facial recognition to monitor GCHQ's existing targets, and to identity new ones.

Nick Pickles, the director of the civil liberties campaign group Big Brother Watch, said intercepting and taking photographs from millions of people's webcam chats was "as creepy as it gets".

"We have CCTV on our streets and now we have GCHQ in our homes. It is right that the security services can target people and tap their communications, but they should not be doing it to millions of people. This is an indiscriminate and intimate intrusion on people's privacy."

Pickles said it was a further example of how the legal and oversight regimes for the security services had failed to keep pace with technological advances.

"It is becoming increasingly obvious how badly the law has failed to keep pace with technology, and how urgently we need a comprehensive review of surveillance law and oversight structures.

"As more people buy technology with built-in cameras, from Xbox Kinect to laptops and smart TVs, we need to be sure that the law does not allow for them to be routinely accessed when there is no suspicion of any wrongdoing. Orwell's 1984 was supposed to be a warning, not an instruction manual."

Carly Nyst, Privacy International's legal director, said the revelation underlined the importance of democratic societies being able to limit the activities of intelligence agencies.

"Today we've found out that the way we now use technology to stay in touch with friends, family and loved ones means many of our most private thoughts and experiences are available for viewing by GCHQ. How can collecting and storing these intimate moments possibly help protect national security?

Alex Abdo, from the American Civil Liberties Union, described the revelations as "truly shocking".

"[It] underscores the importance of the debate on privacy now taking place and the reforms being considered. In a world in which there is no technological barrier to pervasive surveillance, the scope of the government's surveillance activities must be decided by the public, not secretive spy agencies interpreting secret legal authorities."