The number of untaxed cars being clamped or crushed is soaring after a fleet of camera-carrying vans were sent out to catch offenders.

In the 12 months to April, more than 4,500 vehicles were seized by NSL, the national parking and traffic enforcement company hired to clear rogue drivers from the streets - an average of one every two hours.

The figures show a 20% rise on the 3,760 seized in the 12 months before that.

Tim Cowen of NSL, which clamps and remove vehicles on behalf of the DVLA, said: ““We are delighted to be able to assist DVLA and the Department for Transport to reduce road tax evasion.

“Around 70% of the vehicles we clamp or remove are linked to other crime and routinely we find cars with no MOT or insurance, which are a significant hazard to the majority of law abiding drivers in the UK.

“Getting that sort of vehicle off the road is a valuable public service.”

The cars without tax were identified by NSL drivers travelling across the country in vans fitted with cameras which scan number plates and automatically compare them to records held on the national databases to see if they are being driven illegally.

Offenders have their vehicles clamped and have 24 hours to pay a release fee of £100. They must then pay off any back tax due.

Vehicles will be towed away and impounded if not claimed within 24 hours.

For impounded vehicles the release fee increases to £200 and a storage charge of £21 per day is levied.

Unclaimed vehicles can be disposed of either by sale at auction, dismantling or by crushing.

Bethan Beasley, from DVLA’s Enforcement Directorate, said: ”It’s never been easier to tax your vehicle – there is just no excuse not to. Taxing online or by phone is quick, easy and convenient, as it only takes a few minutes to do.”

As well as having drive-by cameras on the look out for tax evaders, Sussex Safer Roads Partnership is now asking residents to report them in the same way as they would antisocial behaviour.

It has created the Operation Crackdown website so people can log on and report tax evaders on the road at www.operationcrackdown.org.

Neil Hopkins, from the partnership, said: “By using Operation Crackdown in this way, residents can make a genuine difference to the roads of their county by helping Sussex Police to crack down on illegally operated vehicles.”