GREENS' claims that there is no scientific proof coal-seam gas is better for the environment than coal have been undermined.

The expert report finds the carbon footprint of generating power from gas is up to 87 per cent smaller than that from coal, The Australian reports.

The findings have provoked charges of hypocrisy against the Greens for opposing CSG exploration and production, while urging immediate action to reduce greenhouse gas emissions that contribute to climate change.

The report by global engineering consultancy WorleyParsons compares greenhouse gas emissions associated with Chinese power generators using Australian liquefied natural gas derived from CSG with those using imported black coal.

It compares the gas and coal technologies across their entire "life cycle" - from extraction, to processing, to transportation and then power generation.

The report concludes: "CSG is significantly less greenhouse gas-intensive for most existing, commonly employed, end-user combustion technologies and for most of the life-cycle scenarios considered."

The report, which will be officially released today, was commissioned by the Australian Petroleum Production and Exploration Association, an industry lobby.

It concedes extraction of CSG carries higher emissions than extraction of coal but says this is more than compensated by the cleaner burning properties of gas.

As a result, 4.3 tonnes of global carbon emissions are avoided for every tonne of carbon produced in CSG-LNG production and use when gas is used instead of coal in a Chinese power station.

The findings come amid increasing controversy surrounding CSG.

Federal independent MP Tony Windsor, whose support is critical to the survival of the Gillard government, has called for a moratorium on exploration.

Farming groups believe the extraction of CSG from underground coal beds can release toxic chemicals into groundwater supplies and prime agricultural soil.

The report by WorleyParsons, which provides services to the petroleum industry, also casts doubt on claims in August by federal Greens leader Bob Brown and his deputy, Christine Milne, that the jury is still out on the relative greenhouse merits of gas and coal-fired power generation.

At the time, Senator Brown questioned Treasury modelling on the carbon pricing package that he negotiated with Julia Gillard, which assumed a huge increase in gas-fired power generation.

"The presumption that the damage done by gas is half that done by coal is under very serious questioning," Senator Brown said.

"The information base is still very shaky."

Senator Milne said in August that rather than transitioning through gas, Australia should "move straight to renewables".

She said the Greens saw gas "at the maximum as a bridging fuel" and challenged the government to produce research to back the claim gas was cleaner than coal.

Senator Milne and Senator Brown did not respond to questions from The Australian last night.

APPEA boss Rick Wilkinson said yesterday the findings of the report proved the Greens, and other anti-fossil fuel activists, "have in recent times developed a blind spot when it comes to the gas industry's greenhouse gas benefit".

"Gas is widely accepted as a cleaner energy source than coal on all counts," Mr Wilkinson said.

"The Greens' opposition to CSG is a political stance. The Greens are not about finding solutions to meeting the energy challenge - just about making noise.

"What the Greens fail to acknowledge is that the industry they oppose offers the most significant, cost-effective and practical response to the risk of climate change."

A peer-reviewed paper by University of Adelaide climate scientist Tom Wigley, published in August, said while gas-fired power production produces about half as much carbon as coal, the difference becomes negligible "where a percentage of the gas production is assumed to leak into the atmosphere".

However, the WorleyParsons study found coal could compete with gas on greenhouse emissions only when the cleanest coal technology was compared with the dirtiest gas-fired plant.

On average, compared with three progressively more efficient forms of coal-fired power, electricity produced by state-of-the-art gas generation was 87 per cent, 51 per cent and 43 per cent cleaner, across the fuels' life cycles.

The finding means that over the 30-year life of a gas-fired baseload power station operating in China, 968 million tonnes of CO2 - almost double Australia's current total annual greenhouse gas emissions - are avoided.

NSW Greens upper house MP John Kaye said gas offered a 50 per cent reduction in emissions, but this was "an unacceptable outcome compared to renewables, which reduce emissions to zero".

"Gas is an energy dead-end that will absorb money and distract from the ultimate objective of a zero-emissions electricity sector. All that 50 per cent buys you is a doubling of the time until you destroy the planet," Dr Kaye said.

Friends of the Earth spokesman and anti-CSG activist Drew Hutton questioned the findings of the report and said there was "plenty of research" to suggest coal and gas were comparable on a greenhouse basis.

"Gas is a fossil fuel and its footprint is not likely to be so far below coal that it will produce meaningful reductions in global greenhouse gas emissions. The big challenge is how quickly we go from coal to renewables," he said.

Read more at The Australian.