New figures from the Society of the Irish Motor Industry (SIMI) show that total new car registrations rose by 7.4% in September to 3,428 from 3,192 the same time last year.
But the SIMI figures show that new car registrations so far this year are down 7.5% to 113,958 compared to 123,195 the same time in 2018.
SIMI said that imported cars in September saw an increase of 20.3% on the same month last year to reach 8,494 and so far this year imports are up 6.7% to 82,432 from 77,278 the same time last year.
Meanwhile, new light commercial vehicle registrations increased by 6.2% in September but registrations year to date are down 1.7%
And new heavy commercial vehicles decreased 22.9% last month and are 0.9% higher so far this year.
Brian Cooke, SIMI Director General, said new car sales have fallen in each of the last three years and he said that with Brexit now only weeks away, business risk in the sector is at its highest level in almost a decade.
"In this uncertain business and consumer environment, any taxation increase would only further undermine an already fragile new car market.
"This in turn will endanger both Exchequer Revenues and employment, while at the same time act as a barrier to the renewal of Ireland's car fleet which is key to reducing emissions from transport," Mr Cooke said.
"Our industry can't afford for the Government to get Budget 2020 wrong, as the impact would have far reaching consequences that could extend for many years well beyond 2020," he added.
Today's SIMI figures show that the biggest selling car in September was the Ford Kuga, while the five top car models sold so far this year are the Toyota Corolla, the Hyundai Tucson, the Nissan Qashqai, the Skoda Octavia and Volkswagen's Tiguan.
Meanwhile, the five top selling brands so far this year are Volkswagen, Toyota, Hyundai, Ford and Skoda.