Tony Abbott's insistence that Labor's emissions trading scheme is an expensive exercise in buying and selling an ''invisible substance'' has drawn derision from climate experts and industry. 

As the Rudd government prepares to detail a path from the carbon tax to an ETS a year earlier than scheduled, the Opposition Leader faces claims he is treading his own path back to the ''politics of climate denial and scepticism''. 

Mr Abbott's assertion that an ETS - to be introduced on July 1, 2014, as the government will announce on Tuesday - was a ''so-called market in the non-delivery of an invisible substance to no one'' sparked an immediate backlash, with critics pointing out that former Liberal prime minister John Howard designed a similar scheme.