New car registrations for last month dropped 72.3% when compared to May 2019, according to the latest figures from the Society of the Irish Motor Industry.
1,751 new cars were registered last month, compared to 6,320 in May 2019.
The figures reveal that Covid-19 has heavily impacted on sales, with retailer's showrooms remaining closed until the 18th of May due to the restrictions.
Registrations year to date are down 34.6% on the same period last year.
The commercial vehicle sector has also been impacted.
Light commercial vehicles are down 70% compared to May last year, while HGV registrations are down 69.8%.
Commenting on the market figures, Brian Cooke, SIMI Director General, acknowledged that there will be a "very challenging" period ahead for the Industry.
"Our Industry is grateful to be open for business again. SIMI members continue to implement social distancing and sanitisation measures, in accordance with both Industry and State guidelines, that will protect both their employees and customers against the spread of COVID-19," he said.
Mr Cook called on the Government to support the industry over the coming weeks and months.
"In the short term the State should expedite the safe re-opening of NCT, while also re-instate the Government Grants for Company Electric Vehicle purchases. The key July registration period is fast approaching, and the Motor Industry has commenced promotional activity with a variety of attractive new car offers already announced in order to optimise sales," he added.