The Coalition's ''direct action'' plan to cut carbon emissions may have a hole blown in its $3.2 billion budget by the actions of conservative colleagues in Queensland, the federal government and green groups say.

The Queensland Parliament passed legislation on Tuesday easing land-clearing rules for the state's landowners, opening as much as 2 million hectares of forests and regrowth areas to deforestation, WWF Australia said.

''We estimate that if all of this land were cleared, it could unlock stocks estimated at 369 million tonnes worth of carbon dioxide,'' WWF-Australia climate change policy manager Will McGoldrick said.

The direct action policy now implies an abatement cost of $15 a tonne of CO2 for forestry. If the clearing were to be spread over 10 years, for instance, the Coalition's plan could be up for about $500 million a year - or roughly 50 per cent more than indicated by the policy's original documents.

''This is not [opposition environment spokesman] Greg Hunt's doing,'' Mr Goldrick said. ''But whatever policy comes into force after the next election will have to be able to accommodate these changes at the state level.''