The wait time for an NCT test has passed five months in 31 centres across the country.
Applus, the company who run the service, says 50 new vehicle inspectors were recruited in December, which they say will help reduce demand.
The longest wait time is in Drogheda, where drivers can not get an appointment before August 31st.
Junior Transport Minister Jack Chambers expects wait times to return to normal levels by this summer: "I think the focus now has to be on reducing the wait times and ensuring that we get back to an average wait time of 12 days by May this year."
He is encouraging people who are due to have an NCT to be vigilant, there is a priority waiting list and up to 3,500 cancellations a week.
As of this lunchtime today, 31 of the 49 NCT centres in Ireland do not have an available slot until June.
NCTs are not valid from the date of the test, but rather from when the test was due to take place. It means drivers could find themselves in a NCT centre twice in just seven or eight months.
Junior Transport Minister Jack Chambers says the system will not be changed to address this, but he does expect wait times to decrease dramatically
Applus increased their staff by 70 last year and say their recruitment efforts are continuing to tackle the backlog.