After years of trials, some of which found major failings, the Metropolitan police has announced it will use live facial recognition cameras operationally for the first time on the capital’s streets.

For now, the technology will be primarily used to find suspects wanted for serious or violent crime. But the deployment undoubtedly takes surveillance of all citizens to a new level. At a time when the European Union is considering a temporary ban on the use of facial recognition to safeguard individuals’ rights, the move is incredibly premature.

The Met goes to great lengths to stress that it has taken a “considerate and transparent” approach: deployment will be clearly signposted, limited to a few hours at a time, and officers will hand out leaflets to passersby.

Yet, while the deployment seems small-scale and “targeted”, the technology is inherently indiscriminate. Live facial recognition of the kind the Met is deploying detects all faces on video footage and then compares the faces against watchlists. That’s why some have compared it to a virtual identity parade. When you walk past such a facial recognition camera, you are effectively standing in a lineup, with other pedestrians, alongside those suspected of crimes. Given that the system inevitably processes the biometric data of everyone, live facial recognition has the potential to fundamentally change the power relationship between people and the police – and even alter the very meaning of public space.

The latter is of particular concern if the technology leads to more widespread and invasive adoption, as new technology often does. As Natasha Lomas remarked in TechCrunch, the launch also prepares the ground for the police to “push for wider public acceptance of a highly controversial and rights-hostile technology via a gradual building out process … AKA surveillance creep”.

Adding facial recognition capabilities to CCTV cameras, for instance, would be a game-changer. Suddenly, the police could trace an individual as they moved across the city. They could identify anyone’s whereabouts within seconds.

And the targets may not only be violent threats to the nation. Race equality campaigners, including the family of Stephen Lawrence, have been spied upon; climate activists from Extinction Rebellion were put on an extremism watchlist; and even an elderly party conference heckler found himself held under terror laws.

Facial-recognition CCTV cameras could identify and record who attends a protest. They could automatically flag “suspicious behaviour”, or people who look or act in a certain way, which could be particularly problematic for groups already stopped and searched disproportionately. This isn’t dystopian fiction, but precisely how the technology is already being used in China and elsewhere.

And in many ways the biggest concern, which is strikingly absent from the Met’s announcement, is that most recognition systems still perform best at recognising the faces of white men. Although the accuracy of matches is improving, the risk of errors remains real – particularly for ethnic minorities.

In high-stakes areas such as policing, misidentification can implicate people in crimes they did not commit. Even if the ultimate decision to arrest someone remains with officers, automated misidentification shifts the burden of proof on to the falsely recognised individual, who suddenly needs to prove that they are not who the system says they are.

Meanwhile many significant legal and ethical challenges remain unresolved. The human rights challenge of a Welsh police force’s trial of facial recognition still has an appeal pending. Last year a report by the Information Commissioner’s Office came to the damning conclusion that the current combination of laws, codes and practices is unable to manage the risks that the technology presents. Responding to the Met’s announcement, the ICO repeated its call for the government to introduce a binding code of practice for live facial recognition “as a matter of priority”.

Given all these concerns, why rush to deploy such a controversial technology? Even if it’s legal, that doesn’t mean it’s ethical. And just because a new technology becomes available, that doesn’t mean the police have “a duty” to deploy it, as the Met claimed last week.

What often gets lost in debates about bias and accuracy is that we don’t know if the technology is actually effective in helping to fight crime. In fact, given its inherent risks, live facial recognition would have to be more effective than alternative, less risky measures, such as simply hiring more police.

The sense of urgency with which UK police forces are forging ahead is startling. Live facial recognition is a steep change in policing techniques. To quote the information commissioner once more: “Never before have we seen technologies with the potential for such widespread invasiveness.”

Though the system will not be linked to other official databases, the UK’s history of surveillance is full of examples of mission creep – from spying laws that were used to follow dog walkers, to pupil data that was shared with the Home Office to create a hostile environment for illegal migrants.

As long as the UK lacks a statutory law with a clear and binding code of practice, it simply isn’t ready for the mass deployment of this technology. At the very least, we need to have a genuine public debate. As hard as it may be, democratic governments need to resist the temptation to undermine civil liberties in the name of safety and security. The stakes are far too high.

• Frederike Kaltheuner is a researcher and tech policy expert. She is a 2019-2020 Mozilla tech policy fellow and former director of programme at Privacy International in London