The earthquake and tsunami in Japan, along with the timing of holidays, is thought to be behind a setback last month in the recovery in new car sales which had been under way throughout 2010 and early this year.
New Zealand Transport Agency figures show a 1 percent decline in new vehicle sales in April compared to a year earlier. Passenger car sales were down 7.1 percent, although new commercial vehicle sales were up 22.6 percent.
Year to date sales were still 11 percent ahead of the same period in 2010.
Motor Industry Association chief executive Perry Kerr said some of the market volatility was driven by new vehicle supply constraints as a result of the Japanese quake.
The supply situation was changing daily as the Japanese motor industry moved to address component shortages affecting production in Japan and other markets.
While he had full confidence in the Japanese industry to overcome setbacks relatively quickly, within the next six months some model lines and individual vehicles may be unavailable, Mr Kerr said.
The association also attributed part of the slowdown in new car sales in April to the timing of Easter and school holidays.
The NZTA figures show 4258 new cars were sold in April, down from 4585 a year earlier and from 6079 in March. For the year so far 21,391 new cars have been sold.
Used car registrations, generally imported, were the lowest in 18 months at 6156, while new commercials numbered 1352, up from 1103 a year earlier but down from 2181 in March.
Toyota remained the top new car make, with a 13.2 percent share of the market in April, below its year to date share of 18.6 percent and the 20 percent of the market it had in 2010.
The top model last month was the Suzuki Swift which had 248 sales, swapping with the normally dominant Toyota Corolla, which was second in April with 149 sales.