Christmas shoppers could have their faces scanned in central London this week as part of a police trial.
The Met says it will invite people to take part in testing the technology rather than scanning people covertly.
The trials will be held near Soho, Piccadilly Circus and Leicester Square on Monday and Tuesday.
Privacy campaigner Big Brother Watch has described the use of such technology as “authoritarian, dangerous and lawless”.
In a statement the group said that “monitoring innocent people in public is a breach of fundamental rights to privacy and freedom of speech and assembly”.
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