Now police and industry experts are asking companies to help stamp out the problem, as a solution is proving beyond their control.
Statistics show that a third of accidents involve drivers travelling on business, but the real numbers are much higher, according to Saul Jeavons, head of investigations and risk management at the Transport Research Laboratory (TRL).
Speaking at a safety conference at TRL, he said: ‘If you are driving your own car and you are asked by police, are you going to say ‘I’m driving for business’ if you are not insured for business use?
"In the vast majority of cases, the police take the answer at face value. I suspect the actual percentage of accidents for business use is far higher. The obvious flaw in the methodology is a vested interest in not answering truthfully."
But Jeavons believes it is better to keep going with the current approach – where police ask a driver involved in an accident if they are on a business or personal journey – until a new one can be formulated. He said: ‘The scale of the problem means it’s still worth doing.’
In the meantime, he added, employers could help with the problem by regularly checking the insurance details of employees who use their own cars on business.
But tackling a legal loophole that means thousands of drivers are on the roads while medically unfit could prove more difficult.
Mark Lamb, a senior collision investigator for Kent Police, said many drivers suffering mental health problems or taking powerful medication do not inform their bosses. Failing to disclose a medical condition that affects driving ability is illegal, but the onus is on the drivers themselves to reveal the problem.
However, Lamb said many do not do so for fear of losing their jobs.
General Medical Council guidelines say doctors should break confidentiality and tell the DVLA if a patient is unsafe to drive but refuses to stop, although Lamb said this rarely happened.
Lamb told the conference: "There should be a lot more feedback from doctors to the DVLA. It’s a fundamentally flawed process. There’s a big problem with people driving out there who are unfit due to conditions either medical or mental. Companies are leaving themselves wide open, but there’s nothing they can do about it."