Martha Spurrier, a human rights lawyer, said the technology had such fundamental problems that, despite police enthusiasm for the equipment, its use on the streets should not be permitted.

She said: "I don't think it should ever be used. It is one of, if not the, greatest threats to individual freedom, partly because of the intimacy of the information it takes and hands to the state without your consent, and without even your knowledge, and partly because you don't know what is done with that information."

Police in England and Wales have used automated facial recognition (AFR) to scan crowds for suspected criminals in trials in city centres, at music festivals, sports events and elsewhere. The events, from a Remembrance Sunday commemoration at the Cenotaph to the Notting Hill festival and the Six Nations rugby, drew combined crowds in the millions.