By failing to address the sources of rising greenhouse gas emissions, even the federal government's minimum target of five per cent cuts by 2020 would be likely to spiral out of reach, potentially exposing Australia to punitive action from other nations that are able to meet their targets. A 15pc or 25pc cut by 2020 could no longer be contemplated, passing on much steeper costs into the following decade.

In essence, farmers would be asked to plough carbon back into the ground faster than the coal industry can dig it up, and Abbott's volunteer ''green army'' would be asked to plant trees faster than the timber industry can cut them down.

Some aspects of the policy, such as the $110 million to be spent over four years on regional clean energy hubs and ''geothermal and tidal towns'', would be useful additions to a plan that had either a carbon tax or a carbon trading system with a strong limit on emissions.

Renewed discussion about the role of carbon sequestration in the soil is also welcome, because it has largely been ignored by the government and new research is close to overcoming some the problems associated with measuring soil carbon.

But there are several lines of evidence suggesting Abbott's policy will be incapable of achieving the serious emissions cuts that are meant to be the point of the exercise.

First, there is no overall cap on emissions for heavy-polluting industries. This is far less than even developing nations such as China, India and Brazil, with their much smaller per capita rate of emissions, are proposing.

Second, the plan for managing the emissions of individual businesses is weak, vague and would be difficult to administer. Companies that exceed their ''business as usual'' limits will be made to pay the government an unspecified amount. ''The value of the penalties will be set in consultation with industry,'' the policy states, meaning industry will control the level of fines it incurs. This could be termed a carrot and twig approach.

Third, the focus on subsidising 100,000 more rooftop solar panels rewards one of the least efficient methods for reducing emissions, and would barely have an impact on national greenhouse gas levels.

The opposition has painted itself into a corner by insisting its policy should be cost-free. The $3.22 billion fund it needs will come from public money found through budget cuts in other unspecified areas.