Key independent MP Rob Oakeshott thought fuel should not be subject to carbon tax, positioning him in conflict with Greens members of the multi-party climate change committee.

According to the Greens fuel should be subject to the tax and the community must be compensated for the extra cost, nonetheless, no decision has been made by the committee.

Oakeshott remains unconvinced despite the presence of a variety of options that might make a petrol carbon tax possible.

"I guess I'd be on the starting side of it being out," Mr Oakeshott told Radio National. We don't have a lot of public transport on the mid north coast of New South Wales. We're not unique in that - there are plenty of parts of a big country which rely heavily on fuel to do business and to live life," he explained.

Greens Deputy Leader Christine Milne conveyed it is proper to have the "broadest possible coverage" for an emissions trading scheme, and "that would include transport".

"The extent to which the price impact will be passed on to consumers is a point of debate and that's something that has not been decided," Milne said in a radio interview.

"We need people to drive less and drive more efficiently and that is the context we'll be bringing to this. We think it's time we invested heavily in public transport and in cars which are more fuel efficient," she said.

Government reports show a price of $40 a tonne is needed to encourage electricity generators to shift from coal to gas-fired power stations.

Climate Change Minister Greg Combet articulates the carbon price will be "well south of that" but the Greens say the $40 mark is "about right".

The committee is expected to decide on the carbon price and other details, including compensation, by early July. "We are now down to the raw, pragmatic, political end of the spectrum of how we get something through this parliament," Oakeshott said.