The warning comes as the Government investigates introducing a complete ban on the use of hand-held mobile phones in cars, which would lead to a boom in demand for hands-free systems.
Independent tests carried out by the Motor Industry Research Association also reveal that work done by car manufacturers to ensure the safety of vehicle occupants in the event of an accident could be severely compromised by some car phone kits.
According to the research metal brackets used in some hands-free kits fail to meet European legislation designed to prevent them causing severe lacerations in the event of an accident.
Employers are being urged to check that their systems meet EC safety standards, including ECE Regulation 21. Phone kit suppliers say the findings provide worrying reading and should encourage a rethink among employers.
Glen Hale, technical manager at telecommunications provider Neatcom, said: 'The results of the tests are extremely worrying. Motor manufacturers invest huge sums of money to ensure that the passenger compartments of their vehicles are as safe as possible. I am certain that motorists will be unaware of the potential dangers posed by fitting metal brackets instead of custom-engineered mounting consoles.
'Employers could face expensive personal injury claims from their staff following an accident because of this problem, but there is only a small price to pay for peace of mind.'
Neatcom manufactures consoles for fleet models including VW Group, BMW, Mercedes-Benz, Ford, Lexus, Jaguar, Renault, Saab and Mitsubishi.
The firm also claims its consoles can be removed easily to avoid damage to the vehicle's central console from mountings. Such damage might lead to lower residual values at disposal time.
Hale said: 'For a small price, owners can improve safety and it really is a very small price to pay for peace of mind.'