The number of new private cars licensed for the first time fell by 1.6% to 26,668 in January of this year compared to the same month last year.
This marked the first fall in new car sales in the month of January for the first time since 2013.
But figures from the Central Statistics Office show that the number of used (imported) private cars licensed in January of this year was 6,798 - a jump of 76.7%.
Car sales last year returned to the level last seen in 2008, but the sharp fall in the value of sterling against the euro following Britain's vote to leave the European Union last June has made the importing of used cars from the UK more attractive.
It would appear than rather than Irish households pulling back on big ticket purchases, some have substituted to cheaper UK imports, Davy Stockbrokers noted.
Meanwhile, the number of new goods vehicles licensed in January 2017 was 3,016, an increase of 8.1%, as the Irish economy continued to grow.
Today's CSO figures also show that 65.1% of all new private cars licensed last month were diesel.
They also reveal that Toyota was the most popular make of new private cars licensed in January, followed by Ford, Hyundai, Volkswagen and Nissan.
Together these five makes represented more than half (52.5%) of all new private cars licensed, the CSO said.
Licensing differs from registration in that a vehicle is licensed when a valid motor tax disc is issued for the first time. Registration occurs when a vehicle gets its registration number for the first time.
The Society of the Irish Motor Industry has forecast that new car sales will fall 3% this year compared with a jump of 18% last year when the economy probably grew faster than any other in the EU for the third successive year.
Economic growth of 3.5% is still forecast for 2017 despite the challenges Brexit poses to vulnerable parts of the economy such as the motor industry and exporting.
The Central Bank said last month that there had so far been a muted overall impact from their near neighbour's impending EU exit.