Facial recognition is being extensively deployed on privately owned sites across the UK, according to an investigation by civil liberties group Big Brother Watch.
It found an "epidemic" of the controversial technology across major property developers, shopping centres, museums, conference centres and casinos in the UK.
The investigation uncovered live facial recognition in Sheffield's major shopping centre Meadowhall.
Site owner British Land said: "We do not operate facial recognition at any of our assets. However, over a year ago we conducted a short trial at Meadowhall, in conjunction with the police, and all data was deleted immediately after the trial."
The investigation also revealed that Liverpool's World Museum scanned visitors with facial recognition surveillance during its exhibition, "China's First Emperor and the Terracotta Warriors" in 2018.
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The museum's operator, National Museums Liverpool, said this had been done because there had been a "heightened security risk" at the time. It said it had sought "advice from Merseyside Police and local counter-terrorism advisors" and that use of the technology "was clearly communicated in signage around the venue".
A spokesperson added: "World Museum did not receive any complaints and it is no longer in use. Any use of similar technology in the future would be in accordance with National Museums Liverpool's standard operating procedures and with good practice guidance issued by the Information Commissioner's Office."
Earlier this week it emerged the privately owned Kings Cross estate in London was using facial recognition, and Canary Wharf is considering following suit.
Information Commissioner Elizabeth Denham has since launched an investigation, saying she remains "deeply concerned about the growing use of facial recognition technology in public spaces, not only by law enforcement agencies but also increasingly by the private sector".
The Metropolitan Police's use of the tech was recently slammed as highly inaccurate and "unlawful", according to an independent report by researchers from the University of Essex.
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Silkie Carlo, director of Big Brother Watch, said: "There is an epidemic of facial recognition in the UK.
"The collusion between police and private companies in building these surveillance nets around popular spaces is deeply disturbing. Facial recognition is the perfect tool of oppression and the widespread use we've found indicates we're facing a privacy emergency.
"We now know that many millions of innocent people will have had their faces scanned with this surveillance without knowing about it, whether by police or by private companies.
"The idea of a British museum secretly scanning the faces of children visiting an exhibition on the first emperor of China is chilling. There is a dark irony that this authoritarian surveillance tool is rarely seen outside of China."
Carlo urged Parliament to follow in the footsteps of legislators in the US and "ban this authoritarian surveillance from public spaces". ®