The motoring lobby is fighting a Federal Government proposal to let people buy new cars online directly from overseas dealers and manufacturers.
The car industry has lashed the Government's claims the proposed "click and drive" model could save consumers money.
The proposal is in a discussion paper for a review of the Motor Vehicle Standards Act and has in-principle support from Assistant Infrastructure Minister Jamie Briggs. But he does not want the option for second-hand cars.
At present, heavy restrictions mean only about 3000 cars are imported by individuals into Australia each year.
Victoria Park dealer John Hughes said the change would not offer savings because new car margins were tight in Australia - one of the world's most competitive car markets.
However, he said it might offer savings on luxury vehicles.
But Motor Trades Association chief executive Stephen Moir said this was unlikely even at the top end. He said individual buyers would lose the freight benefits of bulk imports and local dealers would not cover warranties.
_The West Australian _looked at the sums for a Porsche Cayenne S and found locals might get one thousands of dollars cheaper from Britain.
The official Porsche website shows the model sells in Britain for about $105,000 (Â£60,000), including a 20 per cent local VAT.
The same model in WA costs about $158,000, including more than $25,000 for the luxury car tax.
Mr Moir said buyers would be slugged a further 5 per cent import tariff and 6.5 per cent in stamp duty.
After accounting for differences in tax, tariffs and duties, importing the car would cost about $110,000.
Mr Moir said uncertain costs, such as freight and insurance, would further narrow the gap.
He believes it was an unfair comparison because Porsches sold in Australia met higher specifications with more equipment than in a standard European model.
He said there could be unknown costs in the proposed system, possibly including a compliance test fee.
Comparisons between cheaper cars manufactured and sold directly from Japan with those from local dealers showed little or no savings.
Suzuki estimated freight costs for a car at about $1000 from Japan to Australia.