Studies have shown that almost a quarter of fleet drivers do not check their vehicles with many unaware they need to.
James Sutherland, managing director at Peak Performance, which carried out the research, has urged fleets to enforce vehicle checks as part of company policy.
He said: 'We advise all our clients to have, as a written- down and enforceable part of their company vehicle policy, the duty of drivers to be responsible for carrying out regular checks on their vehicles. Non-compliance should be treated as a serious matter.'
Some fleets are leaving checks until the one-year or 20,000-mile service, which is too long, according to Peak Performance. The research also showed that one in 10 vehicles had such low oil levels there was a risk of engine seizure.
Sutherland said: 'This study shows there is considerable cause for alarm about the safety and condition of a significant proportion of company-owned vehicles on our roads.
'Clearly, it is insufficient to rely on normal servicing to check important fluid levels, tyres and carry out other checks, as service intervals especially on modern cars continue to get even further apart. But it seems a sizeable proportion of company car drivers are doing just that.'
Of the 1,000 company cars checked, 107 had tyre problems such as illegal tread depth and tyre rim damage. Tyre pressures also caused concern as 25% of tyres checked were either under or over-inflated.
Tony Ingram, AA Tyre Fit's training development manager, said this was a major concern for tyre fitting companies.
He said: 'Fleets do not check tyres and tyre pressures enough. They wait until the 20,000-mile service and tyres both wear and deflate before this. Tyres are the number one wear component that compromises safety and by not checking them on a regular basis it can mean more costs for fleets.'
Long service intervals get the blame
LONGER service intervals mean millions of motorists are running the risk of their cars suffering mechanical failure.
Analysis by Comma Oil of more than 3,000 different models shows the average oil sump is just 4.5 litres and, although a typical service interval is 12,000 miles, some cars equipped with 'intelligent service' systems run more than 20,000 miles between oil changes or top-ups.
A spokesman said: 'How much oil an engine uses is dependent on a variety of factors, including cold starts, ambient temperature and distance travelled. As a result, the need to regularly check oil levels and, more importantly, top up in between annual garage visits is even greater. We estimate that at any one time one in four cars on the road need to be topped up.'