New figures from the Society of the Irish Motor Industry show that new car registrations for the month of November were down 9% to 687 as the industry prepares for sales of 181 cars in January.
SIMI said that new cars registrations so far this year slowed down by 10% to 131,200 compared to the same time in 2016.
However, used imports continue to remain ahead with registrations for the month of November up 8% to 7,952.
So far this year, used imported sales are 32% higher at 87,929 compared to a figure of 66,463 the same time last year as sterling weakness encouraged people to buy second hand cars in the UK.
SIMI's director general Alan Nolan said that 2017 was a year of uncertainty for the car industry, as it experienced the impact of Brexit.
"Sterling weakness is contributing to increases in used vehicle imports which continue to influence used car values making Irish used cars cheaper but increasing the cost to change for car buyers which has impacted on new car volumes," Mr Nolan said.
"Although new car registrations have declined and are likely to decline again in 2018, the industry overall has had what can be described as a reasonable year when considering previous registration totals in recessionary years," he added.