The average price of a new car is down 4.7% on last year.
The Society of the Irish Motor Industry (SIMI) / DoneDeal Report shows petrol prices are up 14.3% and diesel rose by over 18% for the first quarter of the year.
Economist Jim Power says consumer behaviour remains relatively cautious: "New used imports from the UK are up by 56.1% in the first quarter and that is undoubtedly undermining used car sales.
"However there is also a lot of increases feeding through in what are necessities for many people, and these increases are undermining disposable incomes."