Motorists caught using a radar or laser speed-camera detection device will soon risk a fine and penalty points on their licence.

Under the Road Safety Act 2006, it will become an offence to have in use or fitted in a vehicle, a device capable of identifying or jamming a speed detection device.

There has been a lot of confusion and misinformation concerning these devices over the years.

It was widely believed that they were already illegal to use in the UK. But in fact this has not been the case and politicians have battled for years to ban the devices, said Andrew Howard, head of road safety at the AA .

As the detectors have been legal, sales have been brisk and thousands have been sold to motorists.

The sophisticated Gatso radar or laser-based detectors should not be confused with ordinary satellite navigation systems. These will remain legal because they use GPS and published mapping technology to warn of published camera sites.

But the devices to be banned can tell in real time which cameras are dummies or have no film. Some devices can also detect mobile sites and laser speed guns used by the police.

However, sat nav users should be aware that some devices come bundled with illegal plug-and-play Gatso or laser speed detection capabilities.

Mr Howard also warned that a sat nav system legal in the UK may be illegal in some European countries.

He said the AA has recently learned that there could be problems if the GPS database has information on speed cameras in some European Union member states.

"We are checking that the AA database doesn't contain these details but I have yet to hear back. Because the databases are produced by only a few companies, it is possible that the information could be contained without anyone knowing," he said.

Quite how the police will be able to tell if someone is using a banned device is not clear. The Association of Chief Police Officers (ACPO) said that as the Bill was still going through parliament, it had no comment to make on the subject.

However Andrew Howard admitted it would be a steep learning curve for the police to identify illegal devices when the Bill finally becomes law.

"I am sure they will come up with some cunning ways to detect them," he said.

Meanwhile, one company is offering a full refund to customers who want to return banned devices, and will upgrade them to a new legal satellite navigator and camera spotter.

Carparts Direct said that customers who bought the products in the past six months will get the £199 replacement device free. Those who paid more than six months ago get 50 per cent off the cost.

Car Parts Direct spokesman Mark Cornwall said: "Customers bought radar detectors in good faith, when they were legal to use. Now the government has banned them, thousands of motorists are out of pocket and with no protection against cameras. We did warn that radar detectors could be banned, but we feel obliged to offer our customers support."

The offer is expected to run for a few weeks, with 500 Rossini Navigator units allocated for the promotion.