"This includes victims, potential witnesses, people with mental health problems, or possible friends of any of those people. It is an atrocious policy and a hammer blow to privacy and liberty in our country," she said.

"Parliament has never debated facial recognition or passed a law allowing it to be used. The public wants police to catch criminals but no one wants dangerously inaccurate tech turning our streets into police line-ups."

She added that the government "should ban live facial recognition until it has properly considered the extraordinary risks it poses to rights and freedoms in Britain".

Technology changes 'the way we move through public spaces'

According to the College of Policing, live facial recognition "turns a digital image into a numerical value before comparing it with images on a police database" which should be chosen each time the technology is used.

It has so far been trialled by a small number of police forces to "detect crime and keep people safe" but critics have privacy concerns over its wider use.

Emmanuelle Andrews, policy and campaigns manager at Liberty, a campaigning organisation, said the guidance "does not solve the underlying problem that facial recognition technology does not make people safer".

Are police illegally using facial recognition technology?

She said it "collect sensitive biometric data from everyone that passes through the camera, fundamentally changing the way we move through public spaces".

"The safest, and only, thing to do with facial recognition is to ban it."

According to David Tucker, head of crime at the College of Policing, facial recognition "will help police catch some of the most dangerous offenders including stalkers, terrorists and others that the public want off our streets".

He said: "It will be used overtly and unless a critical threat is declared, the public should be notified in advance on force websites or social media about its use.

"We hope that those with concerns about this technology will be reassured by the careful safeguards we've set out as requirements for the police who wish to use it, based on a consistent and clear legal and ethical framework across all police forces."

According to David Tucker, head of crime at the College of Policing, facial recognition "will help police catch some of the most dangerous offenders including stalkers, terrorists and others that the public want off our streets".

He said: "It will be used overtly and unless a critical threat is declared, the public should be notified in advance on force websites or social media about its use.

"We hope that those with concerns about this technology will be reassured by the careful safeguards we've set out as requirements for the police who wish to use it, based on a consistent and clear legal and ethical framework across all police forces."