A police force must stop using number plate recognition technology after a warning from the UK's data watchdog.
The Information Commissioner's Office said Hertfordshire Constabulary's use of cameras in and around the town of Royston was in breach of the law.
"It is difficult to see why a small, rural town such as Royston requires cameras monitoring all traffic in and out of the town 24 hours a day," said Stephen Eckersley, the ICO's head of enforcement.
"Royston police decided to track everyone without any clear reason," said Privacy International executive director Gus Hosein.
"Just because a technology enables mass surveillance, that doesn't mean that it is right to do so."
www.bbc.co.uk/news/technology-23433138