Over 1,500 cars tested by the NCT across the Northern Sound region were dangerously defective.
That's according to figures released by the service for vehicles tested so far this year.
A total of 18,000 tests took place across test centres in Cavan and Monaghan since January.
Only 45 per cent of those vehicles passed the test, with the remaining 55 per cent of all cars receiving a "fail major" or "fail dangerous" result.
Across the two counties, 1,548 cars failed because they had a severe flaw that posed a direct and immediate risk to road safety.
The highest number detected was in Cavan, at a total of 786 tested cars.
The Irish Independent is reporting only ten counties in the country have a pass rate of over 50 per cent - with counties Cavan and Monaghan all under 46 per cent.
Research from the Road Safety Authority last year showed 21 per cent of vehicles involved in driver fatalities between 2016 and 2020 had at least one defect recorded by a forensic collision investigator, with 13 per cent of these having defective tyres.
