Nigel Underdown, head of customer relations at Bank of Scotland Vehicle Management, claims the trend of giving employees responsibility for their own cars, including maintenance and insurance, is dangerous when they will be driving on company business.
Employers are under immense pressure to prove they are meeting their duty of care to drivers on business.
Areas of responsibility include ensuring employees are insured to drive a car on company business, that it is 'fit for purpose' and that the employee is skilled enough to drive the business mileage being required.
Underdown added: 'Very few employers bother to inspect owner-drivers' insurance policies, which should be carried out on an annual basis along with driving licence checks.
'Even a secretary making a daily trip to the post office is considered to be driving on business, but few employers acknowledge this. To remove the risk of prosecution to both employer and employee, I suggest that it is in companies' best interests to completely ban the use of private cars for business use.
'This may seem a draconian reaction but employers have to consider the risk, especially when there is a range of safer options available.'
As alternatives, employees could use pool cars, rental cars or even simply borrow a colleague's company car. Although many employers dismiss the idea of renting in vehicles, calculations carried out by Bank of Scotland Vehicle Management reveal rental is often cheaper than reimbursing drivers for covering business mileage in a private car.
For example, a driver making a 400-mile trip in their own car, being reimbursed at 40 pence a mile, would cost the employer £160, whereas hiring a car would cost £66 including fuel, a saving of nearly £100.
Underdown said: 'There would also be no concerns over insurance or roadworthiness. According to our calculations, the break-even point for short-term hire is about the 90-mile mark.'
Alastair Kendrick, a director with Ernst & Young, is one of the leading figures in the call for companies to consider whether staff use of private vehicles on business is safe.
He said: 'Employers will soon come to the conclusion that it is no longer safe to give cash to employees who are essential users. By doing so they lose control over the type of vehicle that an employee uses and whether it is safe for its intended use.'
Companies involved in supplying cash-for-car schemes and structured personal leasing schemes say a ban on private car use for business is unnecessary.
Richard Schooling, general manager of sales operations at Alphabet, a leading company in the field of personal leasing schemes, said: 'We provide a detailed maintenance programme and fully comprehensive insurance covering business use, but not all schemes on the market would be so thorough.'