The Metropolitan Police is to test live facial recognition in Westminster on December 17 and 18 as part of an "ongoing trial" of the technology.
A mobile deployment of the controversial surveillance software will include covering areas in the vicinity of Soho, Piccadilly Circus and Leicester Square and will be used "overtly", the Met said, with a uniformed presence and information leaflets available to the public.
But privacy campaigners have labelled the technology "authoritarian".
Met Police said the test would run for around eight hours on each day, and all faces on the database used during the deployment are people wanted by police and the courts.
Members of the public could decline to be scanned, The Met confirmed.
Ivan Balhatchet, strategic lead for live facial technology for the Metropolitan Police Service said: "The Met is currently developing the use of live facial recognition technology and we have committed to 10 trials during the coming months. We are now coming to the end of our trials when a full evaluation will be completed.
"We continue to engage with many different stakeholders, some who actively challenge our use of this technology. In order to show transparency and continue constructive debate, we have invited individuals and groups with varying views on our use of facial recognition technology to this deployment."
Privacy campaigners have repeatedly expressed concerns around the use of such technology, labelling it "dangerous and lawless".
In May, campaigners from Big Brother Watch used a Freedom of Information request to obtain figures which showed 98% of "matches" found by the technology during earlier Met Police tests were wrong.
The group now claims new figures show the technology has got worse, with inaccuracies rising to 100%.
Big Brother Watch director Silkie Carlo said: "The police's use of this authoritarian surveillance tool in total absence of a legal or democratic basis is alarming.
"Live facial recognition is a form of mass surveillance that, if allowed to continue, will turn members of the public into walking ID cards.
"As with all mass surveillance tools, it is the general public who suffer more than criminals. The fact that it has been utterly useless so far shows what a terrible waste of police time and public money it is. It is well overdue that police drop this dangerous and lawless technology."
Earlier this week, Rolling Stone reported facial recognition software was used in a kiosk of a Taylor Swift concert in the US and images gathered cross-referenced with a database of the singer's known stalkers.
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