The results showed that 17% of a fleet's servicing, maintenance and repair budget was spent on tyres, although nearly a third of respondents could not provide an accurate figure.
And three quarters of fleet managers questioned failed to monitor tyre costs as part of their work in fleet management, despite the fleet industry spending up to £250 million a year on new rubber.
SmartTire Europe carried out the latest research, in which 43% of managers interviewed were responsible for car fleets, with an average fleet size of 1,258 vehicles.
The report revealed that tyre wear and the costs involved in replacement are some of the greatest concerns facing fleet managers, despite their lack of knowledge of the costs involved, but none of them associated tyres with fuel consumption.
Underinflated tyres can cause a 14% reduction in fuel economy, which can blow a big hole in fuel budget forecasts, while tyre life can be reduced by 15%.
Ian Bateman, managing director of SmarTire Europe, said: 'The final finding from the survey is that while tyre-related costs are a concern among fleet managers, very little is being done to monitor or reduce them. Problems such as incorrect tyre pressure represent a serious threat to road safety and fleet budgets.'
SmarTire, a manufacturer of electronic monitoring systems for tyre pressures, also found that only a minority of fleet managers had heard of the devices, which can automatically warn of low tyre pressures.
SmarTire Systems has received Government approval for use in all UK emergency vehicles and has European approval for devices to be fitted to vehicles including cars, light trucks and vans.