POLICE are unable to reveal how many drivers had their licenses revoked during a month-long campaign on driver vision as the information 'cannot be easily retrieved'.

Thames Valley Police teamed up with road safety charity Brake this September, with anyone stopped by officers required to take the 20m number plate check.

Drivers who failed the test had their licenses taken away immediately, but the force admitted there was 'no central record' to check how often this happened.

Responding to a Freedom of Information request from the Oxford Mail, Thames Valley Police said: "Information regarding the taking and passing a request to read a number plate by an officer is unlikely to be recorded.

"A failure of such a request would be held within the free text logs of incidents or occurrences or an officer’s pocket notebook. There is no central record.

"We would therefore have to manually check every incident and occurrence log involving a vehicle offence to determine whether an eyesight test was undertaken and the relevant referral form submitted to the Driver and Vehicle Licensing Agency."

The force added that in September there were more than 1,200 traffic incident reports classified ‘dangerous/erratic driving’. Crashes involving a driver with defective eyesight are thought to cause 2,900 casualties each year on the UK's roads, according to Brake.