The Rudd government's tax hike on luxury cars is losing the support of key crossbench senators.
The tax increase, from 25 per cent to 33 per cent, was introduced in Labor's first budget and is estimated to affect the sales of about 105,000 cars per year.
The tax applies to cars selling for a retail price above $57,180 from July 1.

Independent senator Nick Xenophon has joined the Greens in questioning the sense in making new car buyers pay more for fuel efficient motor vehicles.