The figures are produced in a new survey by fleet and vehicle management specialist Lease Plan.
It found that 64% of large corporates were unsure whether such checks were being made in their workplace.
LeasePlan managing director Kevin McNally said: 'It is worrying that in spite of recent publicity around corporate liability, companies are still not taking insurance matters seriously.
'Where work-related driving is concerned, employers need to think beyond the company car fleet and ensure that insurance is not overlooked when employees are using their own cars for business.'
Company chiefs could find themselves in court facing corporate manslaughter charges should one of their drivers be involved in an accident that causes a death.
The LeasePlan survey also raises concerns that many executives are unaware whether their companies limit the number of working hours that employees spend on the road for business.
A total of 63% of respondents did not know if procedures had been put in place.
McNally added: 'What is alarming about these figures is that employers do not appear to understand the importance of working hours in relation to road safety.
'Although the driver is ultimately responsible for how a vehicle is driven, it is important that the employer is seen to be providing explicit procedures to employees and that there is not an implicit expectation that they should be driving on business for excessive periods.
'Employers must recognise the monetary and legal ramifications of not implementing proper procedures.'
The survey found that the majority of respondents are taking the recent mobile phone legislation while driving seriously.
Since the new law was introduced in December, 88% of respondents said they had implemented, or were currently implementing, new policies.
Companies set up mobile policies
ALMOST all small and medium enterprises (SMEs) have introduced mobile phone policies complying with the ban introduced in December, according to a new survey.
Research has shown that nine out of 10 SMEs have implemented new policies compared to an average of seven out of 10 national UK companies.
Vehicle management group Fleetline, part of LeasePlan, completed the survey which also showed that a third of SMEs have installed hands-free kits into employees' vehicles.
A quarter of SMEs polled said that 25% of employees' vehicles already had hands-free kits installed and 12% were in the process of installing them.
FleetLine director David Harnett said the group had been working with smaller businesses in a bid to promote awareness of the current legislation.
He said: 'FleetLine has been working closely with its SME customers to provide the relevant information and assistance they've needed in order to fall in line with the legislation.
'This includes providing basic guidance on the internal policies that should be drawn up. However, we would recommend that they also seek advice from their legal advisers prior to implementing any policy, in order to ensure full legal compliance.'