Cops in the city have been alarmed by a recent rise in attempts to steal diesel from vehicles.

The suspects are thought to be using tubes to empty fuel tanks of their increasingly expensive contents.

James Pickup, owner of Pickup Skips, on New Brunswick Street, said the thefts were putting more financial pressure on businesses already suffering from increased costs.

He said: "We're having to pay extra for more security because the thieves are always snooping around.

"We've had caps broken off the vehicles' tanks but so far we haven't caught anyone."

Police have also had reports of criminals trying to take expensive catalytic converters from inside engines.

The devices, which reduce harmful emissions, contain precious metals including platinum, palladium and rhodium.

They can be sold on for a very high price as metal prices also continue to rocket worldwide.

DCI Dean Henson, Wakefield district police crime manager, said people should be on their guard against potential thieves.

He said: "Telltale signs include people smelling of diesel who would not probably do so and extra containers being left about along with siphoning equipment.

"We would also like people to report any suspicious activity around businesses where lorries are kept."

He urged drivers to park in well-lit places to deter criminals interfering with their vehicles.

Anyone with information should contact West Yorkshire Police on 0845 6060606.