The UK’s Metropolitan Police Service (MPS) has been authorised to buy and use retrospective facial recognition technology.

The Mayor of London’s Office for Policing and Crime (MOPAC) has approved a contract with Northgate Public Services, a recently-acquired subsidiary of Japan’s NEC Corporation.

The four-year deal is worth £3,084,000, with the technology expected to go into use late this year or early next.

“Technical advancements made over recent years would if seized now allow the MPS opportunities that were not previously available to support the detection and matching of faces,” the decision reads.

“The opportunity also represents a chance to realise significant savings in terms of officer time it takes to reconcile an image of a person to that person’s identity. This helps prevent and detect crime and keeps Londoners safe.”

While live facial recognition – itself extremely controversial – compares live images with those on a specific watchlist, retrospective facial recognition allows police to check against a far broader list.

“These may be images that have been captured by cameras at burglaries, assaults, shootings and other crime scenes. They could also be images shared by or submitted by members of the public,” the decision explains.

The Met says it is consulting with a new body, the London Policing Ethics Panel (LPEP) about governance, and will next month meet the panel to discuss the project.

South Wales Police, which has been trialling the technology, has defended its use. It says a match with a 14-year-old custody photo allowed the force to catch sexual predator Craig Walters, and to identify an unconscious man pulled out of a river.

However, the use of equally-intrusive live facial recognition technology in the UK has already been widely criticised for its infringement of privacy – not least by the Information Commissioner’s Office (ICO).

“When sensitive personal data is collected on a mass scale without people’s knowledge, choice or control, the impacts could be significant,” information commissioner Elizabeth Denham said in a decision earler this year.

“We should be able to take our children to a leisure complex, visit a shopping centre or tour a city to see the sights without having our biometric data collected and analysed with every step we take.”