Cities around the world are scaling up their use of surveillance cameras and facial recognition systems – but which ones are watching their citizens most closely?

Qiu Rui, a policeman in Chongqing, was on duty this summer when he received an alert from a facial recognition system at a local square. There was a high probability a man caught on camera was a suspect in a 2002 murder case, the system told him.

The depth, breadth and intrusiveness of China's mass surveillance may be unprecedented in modern history Maya Wang

The city’s surveillance system scans facial features of people on the streets from frames of video footage in real time, creating a virtual map of the face. It can then match this information against scanned faces of suspects in a police database. If there is a match that passes a preset threshold, typically 60% or higher, the system immediately notifies officers. Three days later the police captured the man, who eventually admitted that he was the suspect.

Cases such as this, where facial recognition systems are used to help local police crack crime cases, are not unusual in the south-west China city, which recently ranked first in an analysis of the world’s most surveilled cities compiled by the UK-based technology research firm Comparitech. With 2.58m cameras covering 15.35 million people – equal to one camera for every six residents – Chongqing has more surveillance cameras than any other city in the world for its population, beating even Beijing, Shanghai and tech hub Shenzhen.

Facebook Twitter Pinterest A young woman is picked out by facial recognition software. Photograph: Axel Bueckert/Alamy

Eight of the 10 most surveilled cities in the analysis are in China. London ranked sixth with 627,707 cameras covering 9 million residents and Atlanta, Georgia, came 10th with 7,800 cameras for 501,178 people.

10 cities with most surveillance cameras per person 10 cities with most surveillance cameras per person

Chongqing, China’s most densely populated city, has been part of the Xue Liang (Sharp Eyes) pilot scheme to tackle crime, which ranks the trustworthiness of citizens and penalises or credits them accordingly. Many crimes committed in a certain area of Chongqing were committed by non-residents, so facial recognition cameras were seen as a way to combat this. According to the Chinese Ministry of Public Security, China is anticipated to have 626m CCTV cameras in use by next year.

But critics warn such widespread surveillance violates internationally guaranteed rights to privacy. To meet international privacy standards enshrined in the International Covenant on Civil and Political Rights, both collection and use of biometric data should be limited to people found to be involved in wrongdoing, and not broad populations who have no specific link to crime. Individuals should have the right to know what biometric data the government holds on them. China’s automated facial recognition systems violate those standards.

Facebook Twitter Pinterest A 3D rendering security camera in an airport. Photograph: PhonlamaiPhoto/Getty Images/iStockphoto

“What we’re seeing is a race to the bottom of privacy among police bureaus in China, with each claiming to be the best and most innovative in carrying out mass surveillance and social control,” says Maya Wang, senior China researcher at Human Rights Watch.

“These systems are being developed and implemented without meaningful privacy protections against state surveillance. The depth, breadth and intrusiveness of the Chinese government’s mass surveillance on its citizens may be unprecedented in modern history.”

Cities elsewhere may not be too far behind China’s mass surveillance. Over the summer, Transport for London used its more than 260 wifi-enabled stations to collect the unique media access control address of users’ smartphone devices, a request sent when a device is searching for a wifi connection, to track their travel journeys precisely. It was only after the media raised awareness of the project that TfL widely informed its passengers.

A few weeks later, it emerged that the private operator of the King’s Cross development in London had deployed facial recognition technology in its CCTV network without express consent or warnings to the public. After public outcry and an investigation by the Information Commissioner’s Office, the programme was scrapped.

“We’ve almost got as many CCTV cameras as China, not quite, but heading that way,” says Paul Wiles, the UK’s biometrics commissioner. “With the rise of things like facial recognition, that is why we need new legislation that decides what is in the public’s interest and the legal structure within which they can be used. We shouldn’t drift there by accident.”

Facebook Twitter Pinterest A Chinese flag flies near a security camera monitoring a traffic intersection in Beijing. Photograph: Mark Schiefelbein/AP

In May, San Francisco became the first major US city to enforce a ban. Supervisor Aaron Peskin, who championed the legislation, said: “This is really about saying: ‘We can have security without being a security state. We can have good policing without being a police state.’ And part of that is building trust with the community based on good community information, not on Big Brother technology.”

Since then, two more Californian cities, Oakland and Berkeley, have also passed bans on all government use of facial recognition technology. Somerville, Massachusetts, passed a similar law this summer.

“I think some cities in the UK may well follow those in the US that have banned facial recognition, or at least call for a temporary halt until we can contemplate legislation,” says Wiles. “Personally, I think the problem with banning is that you then don’t make that crucial decision of whether any of these uses are in the public interest. I would rather see a proper legislative framework and proper trial.”

Some people support facial recognition on the basis that technology has always driven change and is a force for good if used responsibly and proportionately. “The facial recognition technology genie is out of the bottle,” says Stuart Greenfield of Facewatch, the UK’s leading facial recognition company. “If used responsibly by law enforcement and business to assist in reducing crime it is a positive force for good.”

Facebook Twitter Pinterest CCTV sign in King’s Cross, London. Photograph: Tolga Akmen/AFP via Getty Images

However, others are concerned about the number of surveillance cameras and data collection systems included in “smart city” initiatives. “City authorities and the people they serve need to be far more sceptical about whether actually having more data is a panacea for various issues, as well as what additional risks it creates,” says Edin Omanovic, advocacy director at Privacy International.

“The obvious risk is that this only really benefits city authorities and the big tech companies who sell the solutions, rather than the actual people they are purporting to help.”

'We are hurtling towards a surveillance state’: the rise of facial recognition technology Read more

Omanovic argues that live facial recognition fundamentally threatens free societies. “It might start with the monitoring of just a few thousand people but it definitely won’t end there,” says Omanovic. “Authorities need to permanently ban its roll out now before it’s too late.”

There seems to be little sign, though, of cities scaling back surveillance in the near future. “Of all the cities we looked at, the vast majority were increasing their CCTV use or had plans in place to up their surveillance,” says Paul Bischoff, editor of Comparitech.

“Singapore has plans to install 100,000 facial-recognition cameras on lampposts, Chicago police have asked for 30,000 more, and Moscow intends to have 174,000 by the end of this year.”

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