The Rudd government's plan to cut the fuel excise in the first three years of its planned emissions trading scheme is cruel and will disadvantage the poor, the Australian Greens say.

Climate Minister Penny Wong released the Rudd government's green paper on emissions trading, announcing that petrol will be included in emissions trading. She said the fuel excise will be cut so that there is no net increase in price.

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The government said it will review the excise cut after three years. Fuel taxes on heavy vehicle road users will also be cut.

"I think it's actually cruel to give this reduction in fuel excise, because it foregoes the opportunity to put in place the alternatives," Greens climate change spokeswoman Senator Christine Milne said today.

Middle-income earners with two or three cars would benefit most from a cut in the excise, while the poor, forced to use public transport, would be hardest hit, she said.

"The best thing the government could do for Australia is to use the fuel excise to invest in public transport," Senator Milne said.

"What they're doing now is a populist gesture."

ACF says govt missing big opportunities

Meanwhile, the Australian Conservation Foundation (ACF) says it is not good enough to play short-term politics with such a big issue.

"The government has missed a real opportunity to fund things that are a real solution, like public transport and vehicle efficiency," ACF climate change program manager Tony Mohr told Sky News.

"So we would have liked to see the money go towards more long-term lasting solutions rather than a short-term cut in excise.

"Consumers are very concerned about petrol but a small change in excise isn't going to help that."

What was really needed was to make sure vehicles became much more efficient and public transport alternatives were available, Mr Mohr said.

These would make a big difference to petrol bills and emissions. "And we haven't heard from the government what they are going to do about those things so far," he said.

Emissions trading could be in place by 2010 and numerous studies showed it was both achievable and affordable, Mr Mohr said.

"When we compare it to the costs of inaction ... damage to our Great Barrier Reef, our ski fields and our agriculture, it's a clear decision - we have to act to reduce emissions, and we have to do it quickly."

Govt copied Coalition on plan to cut excise: Hunt

The federal opposition has accused the government of stealing its idea to cut the fuel excise, saying it is a cynical approach based on winning the next election.

Liberal leader Brendan Nelson proposed cutting the excise by five cents a litre in his budget reply speech earlier this year.

Opposition environment spokesman Greg Hunt says Labor is "cynically" proposing to cut the excise "but only for a short period of time" to help their re-election chances.

"They attacked us bitterly for proposing it, now they have half adopted it for a sufficient period of time to get them through an election," Mr Hunt told ABC Radio.

"They are proposing a new tax on petrol but they're simply deferring it and in the meantime adopting the mechanism we proposed, outlined and put on the table."

The government was being cynical because they "roundly attacked us (over the excise cut) only weeks ago", Mr Hunt said.

"Right up until very recently we were being scarified."

The Rudd government's plan to review the excise cut in three years did not make sense, Mr Hunt said.

"Either you do it or you don't," he said.