According to AA research, more than 16 per cent of motorists admit to warming their cars on frosty mornings by leaving the engine running.

The AA points out that cars are already disappearing this winter from outside private homes. Says Clare Salmon, managing director of AA Financial Services: “Just before Christmas, 15 cars were stolen in Manchester on one frosty morning – in each case because the engine was conveniently left running, ready to be driven away."

“Car theft using the owners’ ignition keys is a fast growing problem. Locks and immobilisers are becoming increasingly sophisticated so the only way to steal many cars is to use the keys. Thieves welcome icy mornings when so many people simply offer an open invitation for their car to be stolen.”

Some insurers believe that up to one in 10 stolen cars are taken because they have been left unlocked with the keys conveniently in the ignition. According to Home Office statistics, just under half of the 314,000 cars that are stolen in the UK each year are taken from outside their owners’ homes. 12 per cent of all car thefts involve the use of car keys.

And if your car is stolen while it’s warming up, you are likely to get a frosty reception from your insurance company. Says Salmon: “Most car insurance policies will not cover theft of your car if it has been left unlocked with the keys in the ignition yet 14 per cent of motorists in our survey didn't realise this."

“Leaving the engine running to warm the car up while you go back indoors to warm yourself up with a cup of tea is taking a huge risk – it’s amazing how many people do it.”

The AA also warns that petrol stations, car washes and car parks are common targets for car thieves looking for an easy ride by driving cars away using the keys.

The AA offers some simple rules to help you keep your car where it belongs:

• If possible, keep your car in a garage – it will stay frost-free and will start more readily on a cold morning. Lock the garage when you leave.
• If left outside, cover your car’s windscreen with newspaper, cardboard or a shield to keep the frost off.
• Never start your car to warm it up and leave it unattended – this is an offence if the car is on a public road.
• Never start your car to warm up in the confines of a garage – you could potentially gas yourself.
• Keep a scraper and de-icer handy – make sure you clear all of your windows and mirrors before driving off: having obscured glass is an offence.
• If de-icer is unavailable, hot (not boiling) water can be poured over your screen to defrost it – but the water may turn to ice.
• Always lock your car and take your keys with you when filling with petrol, collecting your car park ticket, unloading your shopping, even popping back into your house to collect something you’ve forgotten.