Millions of shoppers had their faces secretly scanned by controversial high-tech cameras looking for criminals, The Mail on Sunday can reveal.

Every visitor to the Trafford Centre in Manchester over a six-month period was monitored by CCTV to see if they resembled anyone on a criminal ‘watchlist’.

In what is thought to have been the biggest UK pilot so far of so-called Automatic Facial Recognition (AFR) technology – which picks faces out of a crowd so that police can arrest that person – Greater Manchester Police supplied about 30 images of missing persons as well as suspects.

Every visitor to the Trafford Centre in Manchester over a six-month period was monitored by CCTV to see if they resembled anyone on a criminal ‘watchlist’ (stock)

But the trial at the centre, which has 30 million visitors a year, was dramatically halted after Surveillance Camera Commissioner Tony Porter warned it was wrong to monitor so many innocent people in the hunt for a handful of suspects.

He said: ‘The police were interested in a tool that could help identify people missing from home and people wanted for crimes. However, compared to the size and scale of the processing of all people passing a camera, the group they might hope to identify was minuscule.’

How tech picks a face from crowd A camera at a pop concert in China spotted a wanted man in a crowd of 60,000 Facial-recognition technology is now so accurate that a camera at a pop concert in China spotted a wanted man in a crowd of 60,000. It works by CCTV cameras capturing the features of every person they see, then comparing them to images of known criminals or suspects stored on a ‘watchlist’. If the system thinks anyone in the live footage matches a person on the list, it sends out an alert and officers can move in. Advertisement

He said it was to the police’s ‘immense credit’ that they contacted him before proceeding further, adding: ‘At this point the police have stepped back from engagement, having recognised that their approach is not currently proportionate.’

While the trial at the Trafford Centre is thought to be the biggest test, other forces have used the technology at specific public events.

Scotland Yard used cameras to look out for known troublemakers at the Notting Hill Carnival, while South Wales Police has deployed AFR at more than a dozen public events including the Champions League final, rugby internationals and even an Elvis festival.

Silkie Carlo, director of civil liberties group Big Brother Watch, said: ‘The lawless growth of facial recognition surveillance in this country is chilling. These identity checkpoints are being quietly rolled out in public places with almost no public awareness, in complete absence of any public debate or even a legal basis.’

Greater Manchester Police confirmed it ‘has had discussions about the potential use of CCTV systems and facial recognition’.