Police will need facial recognition cameras to keep tabs on criminals let loose on the streets under Labour’s justice reforms, Britain’s top officer has warned.

Sir Mark Rowley has called for a major expansion in the use of live facial recognition technology saying police will need it when officers have to deal with more offenders in the community.

The Scotland Yard Commissioner also wants live facial recognition cameras to be installed in crime hotspots and major urban areas like London’s West End to crackdown on persistent offenders.

The force is now planning 10 facial recognition operations a week, trialling the technology at new types of venues, including football matches.

This week the Met won a landmark High Court challenge about the use of the technology, with judges rejecting claims that police broke human rights and privacy laws by scanning faces in public.

Now Sir Mark says there is a ‘mandate’ for expansion in the use of the ‘fabulous’ technology, which will be essential under Labour’s plans to jail fewer offenders by ditching shorter prison sentences and releasing inmates earlier.

Last week Chief Inspector of Constabulary Michelle Skeer warned the Sentencing Act will ‘increase the risk to the public’ as officers struggle to monitor sex offenders left free to roam the streets.

Yesterday Sir Mark said the cameras could assist: ‘It helps us as we’re going to have more offenders in the community, that’s the government policy.

‘Done well, if people are in the community and it’s well supervised and it’s rehabilitative, that could reduce crime.

‘If it’s not done well, then obviously the risks are there with that and time will tell.

‘But we’ve seen how facial recognition can help us in the supervision of offenders.

‘The numbers of registered sex offenders go up every year nationally because depressingly the inexorable numbers of men accessing child sexual content online, who have been arrested every year and added to this register, it’s growing and growing and growing.

‘Our approach to supervising them is largely based on visits to the home address.

‘But surprising them in the street has been really powerful because you find they’ve got a second device they haven’t registered, or software they’re not supposed to have or an automatic delete on their browsing history, which you are not supposed to do.’

Last May live facial recognition cameras spotted a 73-year-old sex offender walking with a six-year-old girl while armed with a knife.

David Cheneler was later jailed for two years for breaching an order banning him from being alone with young children.

Now the Met is investing in more facial recognition camera vans.

The force is also planning to install more fixed cameras after a trial in Croydon town centre led to a criminal being caught every 34 minutes.

The cameras work by taking digital images of passing pedestrians, feeding them into a computer using biometric software to measure facial features.

The image is compared with a watchlist and if a match is detected, an alert is sent to officers to review and consider making an arrest.

If a member of the public is not wanted by police, their biometrics are immediately deleted.

‘It’s really working for us, I see us doing more of it,’ he told the Daily Mail.

‘Facial recognition is a massively powerful tool, it’s reinventing policing.’

Sir Mark also wants to step up the use of drones to capture evidence of a crime scene and help find missing people.

He said: ‘I want to go as fast as possible with the technology as long as we don’t blow up trust on the way because then it’s almost like snakes and ladders as you slip back right to the start because you lose all that trust.

‘I’m leading an organisation that has been shrinking for the last three years and budgets continues to be pressured.

‘There’s no way in the modern world with those pressures and new crime threats that we’re going to stand half a chance if we’re not cleverly using modern technology to get better and faster.’