With the federal election now weeks, not months, away the government now has no choice but to engage in a debate it would rather bury this campaign.

Australian National University professor Andrew Macintosh's attack this week on the government's carbon credit system - describing it as a fraud that is hurting the environment and wasting more than $1 billion in public money - matters a great deal in the context of the looming election.

Polls show there is support for action on climate change across the nation, in both rural and metropolitan communities.

Climate change action also emerged resoundingly as the defining issue of this year's federal election in a national readers' survey conducted by Australian Community Media, publisher of 140 newspaper titles across the nation, including The Canberra Times.

Even before Professor Macintosh, former head of the Emissions Reduction Assurance Committee, went public and called the carbon market overseen by the government a sham, the Coalition's credibility on climate change action was threadbare.

The government struggled even to commit to a net zero by 2050 target, and failed to take to Glasgow anything better than a meagre 2030 goal of cutting emissions by 26 to 28 per cent on 2005 levels. Australia looks increasingly isolated on the world stage when it comes to climate action.

One of the central planks in the Coalition's climate policy, the emissions reduction fund, has always been flawed. It replaced carbon pricing, which proved too politically volatile in Australia, as the federal government's primary means of reducing carbon pollution.

Economists and advocates for climate change action have long pointed out the scheme's problems.

They argue the fund won't achieve even close to the volume of emissions reductions needed to reach net zero, pays for cuts to greenhouse emissions that businesses would have made without the government money, and ultimately involves too little spending for the task of reducing carbon pollution.

Professor Macintosh, who on the assurance committee worked on the integrity of the carbon credit scheme, has cast further serious doubts on it in saying up to 80 per cent of carbon credits issued to projects were "devoid of integrity".

His comments coincide with a new report from The Australia Institute saying the federal government sidelined independent experts and consulted "almost exclusively" with fossil fuel companies and big emitters on rules making carbon capture and storage projects eligible for emissions reduction credits.

The government has targeted the institute with criticisms. For its part, the Clean Energy Regulator has called the think tank's report highly misleading, and insists scientists and technical experts were involved in the process. It has also rejected Professor Macintosh's comments, saying it had worked with independent experts to test his claims and found no evidence to support them.

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Despite the regulator and the government's protests, the thinness of the Coalition's climate change commitments are shaky ground from which to defend itself.

Given the vast sums of money involved, and the fact the government has made the carbon market its major hope of reducing emissions, the questions raised about its mechanism need more than defensiveness and bland, sweeping assurances.

There should be an inquiry.

If the government is so confident in its carbon market, it should have no qualms about calling one.

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