DEVON and Cornwall police could face court action over its network of secret surveillance cameras which read and store millions of vehicle number plates every year.

The Western Morning News revealed last summer that 63.99 million images were taken in 2008 by automatic number plate recognition (ANPR) cameras in the region – the equivalent of two every second and almost a 10-fold increase on the 6.7 million records created in 2007.

Records – even for innocent motorists – are kept on a police database for a minimum of two years. Westcountry MPs complained the network had been expanded "by stealth".

Now it has emerged civil rights group Liberty is planning to launch the first legal challenge to forces' uses of the surveillance system.

"It's bad enough that images and movements of millions of innocent motorists are being stored for years on end," said Shami Chakrabarti, the director of Liberty.

"That the police are doing this with no legislative basis shows a contempt for Parliament, personal privacy and the law.

"Yet another bloated database is crying out for legal challenge and we will happily oblige."

Liberty is now seeking a motorist of good character who objects to having their daily movements stored on the ANPR database to bring a test case.

The WMN revealed that Devon and Cornwall's ANPR files for 2008 equated to 80 records a year for each of the 800,000 registered vehicles in the Westcountry.

Hits on so-called "vehicles of interest" – ranging from those with no insurance to those linked to known criminals – rose from 157,500 in 2007 to 1.16 million last year.

Records not only include details of car registrations, but often photographs of drivers and front-seat passengers.

Devon and Cornwall police said the cameras were essential in the fight against crime – denying criminals use of the roads and catching offenders from drug dealers to uninsured drivers.

Police refuse to say how many ANPR cameras they operate, or where they are installed, for operational reasons. However, they are known to monitor the main routes – such as the A30, A38 and M5 in the Westcountry – as well as other strategic locations such as ports and airports.

Records not of interest to police automatically "drop off" the system exactly two years after they were created.

Shadow Home Secretary Chris Grayling said: "ANPR is a valuable tool to protect us against serious crime and terrorism. But you just can't have a database on this scale without proper accountability and safeguards."