It has emerged that there are now 375,000 vehicles on Irish roads without a valid NCT certificate.
One reason for this is that 3,500 people per week are not turning up for appointments to have their car tested.
Many centres around the country do not have appointments available for the next 5 months.
NCT Operators Applus Automotive is expected later today to 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, as to how and why hundreds of thousands of cars are currently on Irish roads without a valid NCT.
The firm will outline how there are 375,000 vehicles overdue their NCT, which they say is more than double the normal amount for the early months of the year.
The company will be represented at the meeting by its country manager Mark Synnott.
Many NCT testing centres around the country do not have appointments available over the next few months.
The NCT website says they are "experiencing high demand at present and some customers may only see appointments for mid-2023".
The shortest average lead-in time for an NCT appointment is 8 weeks in Carndonagh in Co Donegal while the longest is Northpoint in Dublin which is at 40 weeks. Many centres across the country are facing an average lead-in time of 20 weeks or more.
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