The used-vehicle industry is lobbying to have tough exhaust emissions standards deferred.
The Imported Motor Vehicle Industry Association has written to the Transport Minister asking him to delay the third phase of the standards.
From January, specific requirements on emissions will prevent importers from bringing in Japanese vehicles made before 2005.
The association's chief executive, David Vinsen, says that in itself was expected to cause a drop in imports, but stock shortages resulting from the Japanese earthquake in March will make things worse.
He says the Government should defer the third phase for at least a year. Keeping the status quo, he says, will mean fewer vehicles coming into the country and upward pressure on prices, with people retaining their old cars for longer and the prices of older vehicles going up.
Mr Vinsen says those factors would defeat the purpose of the emissions rule.