The system, which was said to be "top-of-the-line", was being used to spot so-called troublemakers, according to the security company Sophos which quoted a rights group worker who had been invited to view its operation.
The carnival, held in the last week of August each year, attracts about two million visitors.
The company said the system had proved to be useless in 2016 and this year it was worse than that: "it blew up in their faces, with 35 false matches and one wrongful arrest of somebody erroneously tagged as being wanted on a warrant for a rioting offence".
But the Met police viewed the use of the system as a resounding success, Carlos said, because it had come up with a solitary positive match.
Sophos said even this one correct match had some issues. "Even that was skewered by sloppy record-keeping that got an individual wrongfully arrested: the automated facial recognition was accurate, but the person had already been processed by the justice system and was erroneously included on the suspect database."
The company said that of 454 people arrested at last year's carnival, the system was unable to tag a single one as a potential troublemaker.
Photo: courtesy Adobe