LONDON – Police will use facial recognition software to scan the faces of tens of thousands of revellers at this year’s  Notting Hill carnival even though civil liberties groups believe such an action would be discriminatory, according to The Guardian newspaper.

The Metropolitan Police has described the planned deployment as a pilot project intended to look for suspected troublemakers to keep those attending safe.

But critics say the use of real-time biometric tracking has no basis in law and that the plan to deploy it during the carnival is institutionally racist, as it targets Britain’s main annual African-Caribbean celebration.

The Notting Hill carnival is the biggest annual public order test for the Metropolitan Police attracting crowds of up to 1 million people. Police at the two-day west London event will use the facial recognition system and match faces in the crowd against databases of people they suspect will cause trouble, comparing them with images of people previously arrested or under bail conditions to keep away from the event.

At  last year’s carnival 45 officers were assaulted and eight were spat at, requiring them to take medication in case of infection. There were also 454 arrests, the highest number in a decade.

More than 117 million adults included in ‘virtual, perpetual lineup’, which authorities can use to track citizens, raising concerns over privacy and profiling

In a statement explaining its plans, the Met said: “The technology involves the use of overt cameras which scan the faces of those passing by and flag up potential matches against a database of custody images. The database will be populated with images of individuals who are forbidden from attending carnival, as well as individuals wanted by police.”

The Met trialled the system last year, but it failed to pick out any suspects. Facial recognition technology is improving rapidly and the force believes it has the potential to provide a powerful new tool to law enforcement. Only images that come up as a match with a wanted offender will be retained by police, the Met said.

However, as the technology improves and costs come down, it may be the next big battleground between the rights of the individual and power held by the state in the name of public safety.

Martha Spurrier, the director of Liberty, said:” This intrusive biometric surveillance has no place at the Notting Hill carnival. There is no basis in law for facial recognition, no transparency around its use and we’ve had no public or parliamentary debate about whether this technology could ever be lawful in a democracy.”

Stafford Scott, of the anti-racism charity, the Monitoring Group, said: “It is racial profiling. They are coming and putting everyone’s face in the system. A technique they use for terrorists is going to be used against young black people enjoying themselves.

This year’s Notting Hill carnival will be held August 27-28.