The number of new cars sold in July jumped by 51 per cent following the introduction of the 132 number plates, figures from the Central Statistics Office (CSO) show.
There were 9,306 new private cars licensed last month, compared with 6,164 in July 2012.
Of the 9,306 new private cars licensed last month, 2,658 (28.6 per cent) were petrol and 6,539 (70.3 per cent) were diesel.
The top-selling car brands sold during July were Ford (1,441) followed by Volkswagen (1,181), Toyota (836) and Hyundai (794).
Traditionally, more than half of all car sales take place in the first three months of the year, which led to a rather lob-sided business model.
The aim of the new numbering system, which was introduced on July 1st, is to spread new-car sales over the year.
However, the surge in sales in July follows a calamitous decline in June, as consumers delayed purchases in anticipation of the new plates.
The CSO figures differ from those issued earlier this month by the Society of the Irish Motor Industry (SIMI).
The CSO measures the number of cars taxed for the first time while the SIMI figures are based on new registrations issued by the Vehicle Registration Office.
SIMI recorded 11,500 new cars registrations in July following the introduction of the new plates.
The CSO figures show overall new car sales for year was 58,809, down 9.7 per cent on the same period last year, suggesting the industry remained in the grip of recession.
The CSO figures showed the number of used (imported) private cars licensed last month was 4,587 compared with 3,143 during July 2012, which represents an increase of 45.9 per cent.
The number of new goods vehicles licensed last month was 953, down 6.2 per cent on the same month last year.