Jaguar Land Rover is working to beef up car security after a spate of thefts by criminals using equipment bought from eBay to outsmart 'keyless' central locking.

There has been a rise in the numbers of vehicles stolen using the method, with Range Rover Evoques and Sports particularly vulnerable, according to motor insurers' risk analyst Thatcham Research.

Keyless entry kits are marketed on eBay for around £50-£100 and the Birmingham Post found one such device on sale from a Chinese seller.

The executive 4x4s, some built at the Solihull factory, have been hit with a major security breach open to criminals buying the devices.

With the keyless system found online by the Post, full instructions were given for fitting the device to the car, replacing the existing hardware, and allowing it to be driven away.

According to some reports, simple handheld devices are also available to buy, which also get around the locks.

In the first six months of the year, around 300 Range Rover Evoques and Range Rover Sports were stolen in London, Thatcham Research said.

The thieves are then thought to dismantle the cars to remove any electronic tracking devices and ship them to eastern Europe.

A Thatcham Research spokesman said all top-of-the-range cars were vulnerable to keyless thefts, it simply depended which make was on the thieves' latest shopping lists.

He said: "It tends to be organised criminal gangs, a lot of the time from eastern Europe. They ship them out as soon as possible and break them up into parts to sell," he said.

Reports earlier this year suggested that some companies were refusing to insure the high end Range Rovers because of the sheer numbers being taken.

Insurer AIG confirmed that it was requesting extra security measures, particularly in cases where there had been a previous theft, including secure off-road parking.

Police have also warned drivers to invest in the old-style steering wheel locks to try and protect the vehicles.

A spokesman for Jaguar Land Rover, which makes Range Rovers, said the company was introducing a new security measure to tackle the problem.

He said: "This is an extremely serious issue for the automotive industry. At Jaguar Land Rover, we have been working closely with the Metropolitan Police and other forces across the country and this has resulted in a number of prosecutions.

"We have a dedicated engineering team continuously developing new technologies to try to stay one step ahead of criminal gangs.

"So far, three security upgrades have already been implemented this year alone. We are now introducing our fourth upgrade, which we are confident will address the latest theft mechanisms being used.

"Our line-up continues to meet the insurance industry requirements as tested and agreed with relevant insurance bodies.

"Nevertheless we are taking this issue very seriously and our engineering teams are actively working in collaboration with insurance bodies and police forces to solve this continuously evolving problem. This has resulted in a number of prosecutions."

The SMMT, the trade body for manufacturers, said that it was working to develop preventative measures against theft.

"Over the last two years, many vehicle manufacturers have released a series of software updates to help combat keyless vehicle theft and stay one step ahead of thieves," it said.

"The challenge remains that the equipment being used to steal a vehicle in this way is legitimately used by workshops to carry out routine maintenance.

"We need better safeguards within the regulatory framework to make sure this equipment does not fall into unlawful hands and, if it does, that the law provides severe penalties to act as an effective deterrent."