London's Metropolitan Police force's use of "intrusive" technologies "without proper regulation" could put a fundamental principle of policing at risk, the London mayor has been told.
In a letter (PDF) to Sadiq Khan, the Greater London Assembly – the group elected to hold the mayor to account – expressed "significant concerns" about facial recognition technology.
The Met has used it at the two most recent Notting Hill Carnivals, but while it claims this is a trial, it is keeping schtum on the details – even in the face of reports it led to 35 false matches and one wrongful arrest this year.
"This is a hugely controversial topic and it is extremely disappointing that trials have been conducted at the Notting Hill Carnival with so little public engagement," said GLA oversight committee chairman Len Duval in the letter.
Khan and the Mayor's Office for Policing And Crime (MOPAC) have a responsibility to push the Met to improve engagement and transparency, he said.
Duvall added that it was particularly concerning that the trial was going ahead despite the lack of a national strategy on biometrics, which was originally promised by the government in 2012 but has been repeatedly delayed.
"The Met is trialling this technology in the absence of a legislative framework and proper regulation or oversight," Duvall said.
"The concept of policing by consent is potentially at risk if the Met deploys such intrusive technology without proper debate and in the absence of any clear legal guidelines."
He said the committee felt there was "a strong case" for Khan to "instruct the Met to stop trials" until either MOPAC establishes an internal framework or a national one is developed and consulted on.
The GLA also gave short shrift to the Met's attempts to alert the public to its work, saying there was "no indication" it planned to publish any results.
It added: "Simply putting out press releases is not enough: the Met must engage with the public and with stakeholders in a much more meaningful way before going any further."
The group's calls echo those made by the UK Biometrics Commissioner Paul Wiles, who has also called into question the police's use and retention of biometric images.
The GLA referred to this in its letter, criticising the fact there is "no simple way" for people to find out how long their personal data is held by organisations in the capital.
For instance, the Met keeps automatic number plate recognition data for two years, but Transport for London keeps the same data for 28 days. And images from the force's body-worn cameras are kept for 31 days, while TfL retains Oyster journey data for eight weeks.
"This is a very confusing picture and we ask you to consider how the GLA Group can make it easier for the public to find out how long their personal data is retained," Duvall said.
Elsewhere in his letter, Duvall warned the mayor that TfL’s plans to use Wi-Fi connection data to sell advertising risks leaving customers feeling like they "have been taken advantage of".
He said TfL should have made this clearer, and urged it to address it when the data collection is rolled out across the Tube network.
The Home Office didn't respond on the record. ®