As many as two million motorists could be jeopardising their insurance by listing themselves as the main driver on a car in which someone else covers more mileage.

The process, known as 'fronting', secures a cheaper insurance quote for the real main driver who, in many cases, is young or has less no-claims discount. But it is illegal and could completely invalidate the policy and leave the drivers vulnerable to prosecution.

Research from Privilege car insurance has revealed not only that the two million drivers could be risking more than they imagine, but also that ab out one million motorists are named as the main driver on insurance policies for cars they have never even driven at all.

In the event of an accident, if an insurer has enough cause to believe that fronting fraud is evident, any payout could be withheld and the insurance could even be cancelled.

There is also an alarming level of confusion around what level of cover a driver has when they are behind the wheel of someone else's car but are not named on the insurance policy.

Around 21% of car-owners who drive regularly believe that they would be covered for damage to that car, perhaps unaware that the Driving Other Cars (DOC) extension cover does not pay for damage to the vehicle they are driving itself. It is the equivalent of 'third party-only' insurance – the lowest level legally available.

These drivers may be completely unprepared for the bills they will face if they damage the car they are driving.

Also revealed in the study is a worrying trend of people driving friends' or family members' cars without being named on the policy at all, potentially meaning that they are driving completely uninsured.