TWO-THIRDS of cars 10 years or older failed the National Car Test (NCT) on the first attempt this year.
Figures provided by the NCT service show that more than 65pc of cars with 2002 or older registrations had to be retested after major defects were fixed.
Motorists are increasingly holding on to their older cars as they cannot afford to trade them in for newer models.
And many of them are not bothering to have them serviced when this is due, according to the Automobile Association (AA).
The top five reasons for cars failing during 2012 were the condition of the front suspension, followed by defective tyres, incorrectly aligned headlights, defective brake lines/hoses, and broken brake lights.
Results from the NCT testing service for the year, obtained by the Irish Independent, show a 65pc fail rate for 2002 vehicles and older, 49.6pc for 2004 cars, 40pc for 2006 models and 27pc for 2008 cars. Most subsequently passed on a retest.
In 2010, 10-year-old cars had a fail rate of 59pc.
AA corporate affairs manager Conor Faughnan said the NCT figures shed a light on the nature of the national car fleet, which has been ageing over the past few years.
"The fleet is getting older as people are doing less and less vehicle maintenance because of the economic situation," he said.
"For example, people are holding on to their tyres longer, hoping to get an extra winter out of them."
He said that many car owners were not bothering to have their cars serviced when the time came.
"If your car is due a service before Christmas and it's going to cost you €200, a lot of people may just put it off. But this is a habit that will cost you more in the long run over the lifetime of the car," he added.
According to Mr Faughnan, many motorists were also using the NCT test as a diagnostic way of discovering any defects.
After the car failed, they repaired the defects and got their cars passed the second time round.
An analysis of 100,000 breakdown call-outs responded to by the AA found a noticeable increase in the number of puncture-related call-outs compared with the previous two years.
While road conditions were a major factor, the AA said another contributing factor was the fact many motorists were now hanging on to their cars longer these days and not paying enough attention to tyre wear.