One in 10 motorists never performs any safety checks on their cars, according to a new study carried out by garage chain Kwik Fit.
Worryingly, more than a third of drivers (36 per cent) forget their car's first MOT test date and fail to have it checked on time.
With 368,000 cars registered in September 2009, up to 133,000 owners of 59-plate cars risk driving illegally with no MOT, also in the process invalidating their insurance.
A key finding to have emerged from the study is that 3.4 million cars go without safety checks from year to year, making the annual MOT test the only time that they receive any mechanical attention.
Almost half of all drivers (47 per cent) admit that they don't examine their tyres for tread depth or condition, and more than two-thirds of motorists (69 per cent) don't check their brakes between MOTs.
A car's suspension is the most neglected part of the car as 84% never check it, while nearly three-quarters (73%) don't check their exhaust.
These findings underline the importance of the MOT test for road safety, and this month sees the annual peak as more cars require a new MOT in September than at any other time of the year.
September 2009 accounted for a fifth (18%) of that year's new car sales, and these 368,000 cars will be due their first MOT before the end of the month.
Roger Griggs, communications director at Kwik Fit, says: "We were very surprised to see so many drivers admitting that they don't carry out checks on their cars. Areas such as tyres, brakes and lights are key to road safety, so it is vitally important that motorists don't just leave them until the MOT."