One in five motorbikes aren't registered for tax

Although the government collected �4.6bn in duty during the year to April 2003, about �193m was lost through evasion, the National Audit Office said.

The number of people not paying up has risen in seven of the 11 regions in Great Britain in the year to April, with the biggest increases seen in the East of England and Greater London.

Motorcyclists were the biggest thorn in the side of the government - with almost a quarter of bikes going untaxed.

Word of warning

The Driver and Vehicle Licensing Agency (DVLA) is trying a number of tactics to eat into the soaring levels of evasion.

Its tools include wheel clamping, reading number plates, working off reports from police and traffic warden - and publicity.

About 40,000 vehicles were clamped in 2002-2003, a huge increase on the 25,000 vehicles immobilised in the previous year.

But it now seems that many people prefer to lose their car than own up to tax-dodging.

Since the introduction of wheel clamping in 1997 more than 108,000 vehicles have been clamped - and almost seven in 10 of them have been crushed.

The DVLA now says it plans to increase the number of cars it clamps, and intends to triple the number of staff it has working on the initiative in London.

New measures

But aside from these traditional methods of catching the tax dodgers, the DVLA has turned to new technology to enhance its efforts.

One new initiative is Project Laser, which involves using cameras to identify unlicensed vehicles.

Once identified, the vehicle is stopped by a police "intercept" team and the driver interviewed.

One problem for the agency at the moment is having to spot an unlicensed vehicle on the road before being able to bring action.