A leading car manufacturer is to fit a device to stop thieves stealing spare tyres fitted underneath vehicles after a spate of thefts in London.

Most Peugeot cars are designed with spare tyres underneath, and thieves have been using cutters to snap the metal restraining them. Now the company is to launch a device which bolts them to the underside of the car. It will soon be available from Peugeot.

A company spokesman said: 'We sell enormous numbers of cars right across Europe where this problem is practically unknown. And the cars are exactly the same.

'The problem is particularly bad in London because people have to park in the street presumably. The wheels can cost more than pounds 200 to replace. Thieves sell them for between pounds 80 and pounds 100 each.

The trend for external wheels has been forced on the manufacturers of small cars because catalytic converters are taking up more space at the rear of vehicles.

The latest Ford Fiestas, certain Citroen, Vauxhall and Renault cars are usually fitted with external tyres. Suzuki jeeps, which have conspicuously large wheels at the back, have also been targeted.

Ford redesigned its Fiesta this year. All new models will have a more secure spare wheel. A cheaper steel wheel rather than an alloy one will also be fitted. A spokesman said: 'A major change to a car's design isn't something you can do overnight, but we are aware of the problem.

Since 1989 Ford Fiestas have had spare wheels fitted with a metal fastening only. From this year they will be fitted with something akin to a metal tray covering the spare wheel. The spokesman advised owners of the earlier models to contact Ford dealers for ways of bolting the wheel on. 'Alternatively they could leave their spare wheel at home, he said.

'There are pros and cons to having your wheel outside. If it's tucked inside a full car there can also be problems.

'If you're stuck on a motorway at midnight you don't want to unpack the whole car to get the wheel out.