Sales of new cars in September fell 12.26 per cent compared to the same month last year, according to new figures.
The Society of the Irish Motoring Industry said 6,145 sales took place last month compared to 7,004 in September 2005.
Overall year-to-date sales for new cars are 172,052, up 4.12 per cent on the first nine months of 2005.
Sales of light commercial vehicles for the first nine months of the year (36,773) were up 8.64 per cent on the same period last year (33,849), while sales of heavy commercial vehicles this year are 5,282, up 20.21 per cent on the same period last year (4,394).