ALL cars undergoing the National Car Test (NCT) will face strict measures to make sure they aren't 'clocked', under new rules being drawn up by Transport Minister Leo Varadkar.
The Irish Independent has also learnt that 10pc of cars going through the NCT have had their mileage deliberately and artificially decreased.
Department of Transport sources said the high level "suggested there is a problem".
But under new plans, cars will have their mileage cross-referenced with their NCT history every time they go in for the test.
The move is aimed at clamping down on clocked cars being sold on the second-hand market, and to improve road safety.
And it would become a crime to have your car clocked. At the moment, it is a crime only to sell a clocked car.
The idea was touched on in the road safety strategy published by Mr Varadkar last week, but will be fleshed out in the coming months.
The aim is to have the system rolled out within around two years, and motorists would be able to check mileage history.
The odometer of all cars is read when it is put through the NCT, and there are readings for 1.8 million vehicles on file.
The readings were collected from around 2.3 million NCT tests in recent years, but cars which have repeated tests carried out have never had their mileage cross-checked.
Because of anecdotal evidence from consumers and industry experts about clocking, it was decided by the Department of Transport to cross-check the mileage of cars which had already been through the NCT process to establish how common the practice was.
Some 59,528 cars – which had undergone a total of 124,501 NCTs – had their mileage cross-checked.
The cars were either vehicles registered as new in Ireland or which have a first registration date in Ireland on or after January 1, 2006.
Sources said the reason for taking this approach was to "ensure greater reliability in the results, based on readings exclusively in kilometres only".
"Data relating to older and imported vehicles is less reliable, and in the case of imported cars we do not have any previous history details," the source added.
Analysis found that 5,824 had lower mileage readings the second time around.
"That level suggested there is a problem with it," a source said.