Attacked by eco-activists and punished by the tax-man, now the owners of the much-derided 4x4 have a new enemy – thieves who slip underneath their vehicle’s chassis and saw off its catalytic converter.

Police believe thousands of the exhaust parts have been stolen from 4x4s in the past six months by criminal gangs that want the precious metals inside. The converters – which are designed to reduce the toxic emissions from a car’s exhaust – contain platinum, palladium and rhodium. The prices of those metals have soared in the past two years.

The models most targeted include the Mitsubishi L200, BMW X5 and Ford Ranger. Many Mitsubishi Shoguns and Land Rover Discoveries have also been hit. Although the car can be driven to a garage for repair, a loud rattle will be heard underneath the vehicle, similar to the sound of a broken exhaust. The converter costs up to £2,000 to replace.

Peter Tyrell, a crime prevention officer for Lincolnshire police, said: “Four-by-fours are particularly popular with these criminals because they have a high clearance off the ground.

“These people can get under the chassis and saw off the converter in less than three minutes.”

The gangs have also targeted car showrooms. Iain Crighton, a Mitsubishi dealer in Peterborough, said: “We were hit badly. Seven of our 4x4s and two other cars were done in one night.”

The thieves, who sell the catalytic converters on to metal traders for between £100 and £200, are the first stage of an international trade in scrap metal that takes the stolen car parts to India, China and eastern Europe to be recycled and sold on.

Northamptonshire police said some thieves are quite brazen: “They are known to strike in broad daylight in busy areas. In some cases they have been seen using mechanical dollies to slide under vehicles more easily.”