Plans to consult on the proposal to extend the first MOT for new cars from three years to four years prompted industry backlash earlier this month, with major concerns about safety.
However, new doubts from HPI highlight a hidden threat for car buyers.
Neil Hodson, managing director, said: “There are clearly some safety concerns surrounding the idea of extending the MOT period by a further 12 months, but there is also an increased risk of fraud.
“Whilst it’s fair to assume that older cars are the most likely to have their mileage reading altered, the reality is that around a third of all cars checked by the trade with HPI are found to have a mileage discrepancy within the first three years of their life.
“Extending the period for a further fourth year would see the number of pre-MOT cars with a suspect mileage increase, putting used car buyers at significant risk.
“Buying a clocked vehicle poses a real safety threat, not to mention the additional cost of unexpected repairs.
“The proposed extension on the MOT offers motorists savings on one hand, but it could cost them a lot more if it gives clockers a free ride.”