GCHQ, the UK Government listening post, intercepted the web chats of millions of Yahoo customers in a programme codenamed Optic Nerve, it has been alleged.
According to documents shared with The Guardian by Edward Snowden, users who were not suspected of any wrongdoing had their webcam images intercepted and stored by the British intelligence agency, working in collaboration with its American counterpart the NSA.
The Guardian claims the documents it has received show the programme from 2008 until at least 2012 and was being used for experiments in facial recognition.
Those targeted would, without their knowledge or consent, have a freeze-frame image from their chat taken every five minutes and stored by the NSA, the publication said.
It is alleged that in just one six-month period in 2008 the agency collected webcam images "including substantial quantities of sexually explicit communications" from over 1.8 million Yahoo user accounts worldwide.
Indeed, the scale of intimate imagery being collected through Optic Nerve between 3 and 11 per cent was believed to contain "undesirable nudity" led to GCHQ trying to find a way to make it "safer to use".
The revelation that Yahoo's webcam chat facility has allegedly been used as a conduit for broad-based, untargeted spying has provoked a furious response from the internet giant.
In a statement, Yahoo said: "We were not aware of nor would we condone this reported activity. This report, if true, represents a whole new level of violation of our users' privacy that is completely unacceptable and we strongly call on the world's governments to reform surveillance law consistent with the principles we outlined in December.
"We are committed to preserving our users' trust and security and continue our efforts to expand encryption across all of our services."
