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 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.
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%.
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.