Tony Abbott has branded emissions trading a "so-called market" that deals in an "invisible substance", carbon dioxide, as the Coalition digs in politically ahead of Labor's looming overhaul of its clean energy package.

Emissions trading is an internationally recognised market-based mechanism for reducing carbon pollution, and was the policy of the previous Howard government before it lost the election in 2007, but the opposition leader declared on Monday that carbon markets were not true markets because they traded an "invisible substance".

"This is not a true market," Abbott told reporters during a campaign visit in Sydney. "Just ask yourself what an emissions trading scheme is all about. It's a market, a so-called market, in the non-delivery of an invisible substance to no one."

A reporter inquired whether this made carbon markets just the same as financial markets. Abbott repeated his definition: "Let's think about it. It's a market in the non-delivery of an invisible substance to no one."

The opposition leader contended that the world was turning its back on carbon trading schemes and carbon taxes as policy mechanisms for reducing pollution. "Ever since Copenhagen it has been absolutely obvious that the world is not moving towards taxes, whether they are fixed taxes or floating taxes," he said. "The world is moving towards the kind of direct action measures to improve the environment which the Coalition has long championed."

But during a recent appearance on the ABC's Q&A program, the former Liberal leader Malcolm Turnbull appeared to suggest that direct action was a temporary policy for the Coalition on the way to joining other countries that have adopted market-based policies.

The climate change minister, Mark Butler, blasted Abbott's comments on Monday morning. "He has let the cat out of the bag again today. No matter how hard he tries to hide it, Tony Abbott is an economic illiterate and a climate change denier."

Abbott's comments come as the government will unveil details this week of its plan to scrap the fixed price period of the carbon package. Labor says it intends to move to an emissions trading scheme from 1 July 2014 – one year earlier than currently legislated.

The treasurer, Chris Bowen, is refusing to specify ahead of the formal announcement the cost to the budget of removing the fixed-price period. But he has indicated the cost to revenue is in the order of several billions.

The finance minister, Penny Wong, said emissions trading was the lowest cost means of reducing pollution, and she blasted the Coalition's direct action policy alternative.

"That's the whole point of an emissions trading scheme. You set a cap at the limit that you want to achieve and then you let firms work out how they achieve that. They can find the lowest cost way to reduce their emissions," Wong told the ABC.

"It's a market-based mechanism – lower cost for families, lower cost for households. It stands in stark contrast to the kind of Soviet-style scheme that seems to be on offer from [opposition climate spokesman] Greg Hunt and Tony Abbott."

And with new opinion polls showing a federal election held today could deliver Australian voters another knife-edge result, Abbott used a breakfast television appearance to rule out negotiating with any crossbenchers to form a minority government along the lines seen in the 43rd parliament.

"I don't do deals. I do rule it out," Abbott told the Nine Network. "I think that the Australian people are sick of hung parliaments."