Many of the tough-looking yellow steering-wheel locks sold on the promise of protecting your car against theft might as well be made out of Plasticine. In tests conducted for Driving, it was discovered that with a few basic tools and a little know-how a thief could disable many of the most popular locks in less than a minute. One device held up for just three seconds.

For years car-lock manufacturers have boasted that car crime can be cut by simply fitting one of their mechanical locks, and with 350,000 vehicles being stolen every year in England and Wales the public have been keen to do anything they can to deter crooks. Halfords, the motor accessories giant, reported more than 250,000 sales of the devices last year from its stores.

For many car owners whose vehicles are not fitted with electronic immobilisers, steering-wheel locks and gearlever/handbrake locks seem to offer the most effective and visible deterrent to thieves. Electronic immobilisers have been a requirement on UK cars only since 1998, and because about half of the 30m cars on the roads are more than six years old, millions of motorists routinely fit the locks in the belief that they will make their cars immune to theft.

We asked Giles Verdon, a professional car security adviser, to test eight of the bestselling locks. The results were shocking: none of the eight proved to be resistant to attack, only two lasted for longer than two minutes, and five were removed in less than 20 seconds.

Verdon used only basic everyday tools, such as hammers and screwdrivers.

“Manufacturers in general have done little to uprate this type of product for a decade,” he says. “This is bad enough, but the packaging still tells the buyers that it will stop their cars being stolen, which in many cases is patently untrue.”

The tests also showed that you get what you pay for. The cheapest lock, the Hilka Elephant, which retails at just £9.99, was removed in six seconds, while the budget £29.95 Autolok Protector, which attaches to the gearlever and handbrake, came away in an astonishing three seconds without the use of any tools. A large number of these devices have been sold across Europe.

The more expensive locks fared better, but only when compared with the weak opposition. The best was Disklok, which costs £75.99 and took 128 seconds to remove. The Stoplock Ultima, priced £59.99, took 123 seconds to dismantle — with lots of noise and effort.

Both models are designed to cover the whole of the steering wheel, offering greater all-round protection and preventing the thief from simply cutting the steering-wheel rim. Such locks may be big, bulky and awkward to fit but at least they provide some reasonable security.

Verdon’s testing techniques are based on his knowledge of real-life crime. In 1991 he was commissioned to research thieves’ techniques by anti-theft-device manufacturers. His findings were used by Thatcham (the insurance industry’s testing body) as the basis for what became the category 3 standard.

Manufacturers argue the devices are more to deter opportunistic amateurs than hardened professionals. Diana Gritt, a spokeswoman for Autolok, said: “The Autolok Protector is intended as a deterrent. It is not tested against attack.”