The 2002 estimate of the number of unlicensed (i.e. untaxed) vehicles is £1.76 million, of which 161,568 were declared as SORN 1 . This estimate includes £1.19 million vehicles in the car and light van category, of which 104,419 were declared as SORN.
Estimates from the insurance industry are that there are about 1.25 million motorists driving whilst uninsured.
I understand that many of the vehicles which are unlicensed are also uninsured. My Department is currently undertaking research to estimate the number of vehicles that are unlicensed, uninsured and without a valid MoT Certificate.
1 Statutory Off-Road Notification (SORN) is a system by which vehicle keepers who tell the DVLA that they are taking their vehicle off the road are not obliged to tax them.
Vehicle Excise Duty Evasion 2002 published by the Office of National Statistics.