Almost 60% of NCT centres have no test appointment available within the next five months.
As of yesterday evening, nine testing sites had no appointment available until August. The centres are in counties Cavan, Louth, Kildare and Dublin.
Junior Transport Minister, Jack Chambers, acknowledged the impact that long waiting times are having on some drivers and said improvement is badly needed.
"The current waiting list times are totally unacceptable. I know it's very disappointing for many people and is causing anxiety and worry for people who are waiting for a test".
"People expect a proper standard of service. It's meant to be a 12-day average wait time from Applus+ which provides the service on behalf of the Road Safety Authority".
Minister Chambers says extra capacity should see more NCTs completed in the coming months.
"We have seen increased capacity being built over the last summer months.
"We were at 25,000 tests per week in the autumn. That'll be at 35,000 tests per week by the end of this month.
"I've been informed by the Road Safety Authority that the objective and target is to get back to the 12-day average wait time by the end of May of this year."