The Australian Greens want the government to make legislation that aims to hike the tax on luxury cars more climate friendly.
The government has proposed to increase the tax, from 25 to 33 per cent, on vehicles costing more than $57,180.
The Senate is scheduled to debate the legislation today.
Greens leader Bob Brown said the tax hike should be recast as a tax on high-emissions vehicles.
The Greens, who hold five of the seven balance of power votes in the upper house, would try to get the bill redrafted to focus on "gas guzzlers".
"We want the bill made climate friendly," Senator Brown told reporters in Canberra today.