Motor vehicle industry representatives say government regulations on car imports has led to a big lift in the price of used cars.
The Government's vehicle emissions standards which came into force in January mean most cars manufactured before 2005 are not allowed into the country.
Turners Auctions chief executive Graham Roberts says the average price of used cars older than seven years has increased because fewer cars are available following the restrictions.
For example, a used Toyota Corolla from Japan is selling for 70% more than five years ago, he says.
The Motor Trade Association says the restrictions, which were expected to reduce the number of old cars on the road, have in fact driven up the age, as well as the price, of the national fleet.
Association spokesperson Ian Stronach says people are holding onto their old cars for longer.
He says the average age of the fleet has risen from just over 11 years in 2001 to about 13.5 years at present, with much of the gain in the last three years.