3,500 people are failing to show up for their NCT test every week.
NCT Operators Applus Automotive will today apologise to customers for recent booking issues in front of an Oireachtas Transport Committee.
Representatives from the car testing company are set to answer questions from Senators and TDs, including how and why hundreds of thousands of cars are on Irish roads without a valid NCT.
At the moment, 375,000 cars are on the road without a valid NCT, which is 170,000 above the norm for this time of year.
Applus says it's struggling to match capacity with demand.
Applus says the backlogs are partly down to the large numbers of no-shows, and an ageing workforce within the organisation.
Recent figures revealed that almost 60% of NCT centres, of which there are 49, have no test appointment available within the next five months.
