The Government, however, pointed to the public release in October last year of Treasury modelling and then set about branding Mr Abbott as erratic, reckless and unreliable.

Mr Abbott showed no humility. He dismissed the Treasury findings as ''implausible'' and out of date and demanded fresh figures.

Mr Abbott, who has adopted a no-holds-barred approach to Opposition, began the fight on Wednesday when he speculated that if Australia agreed to cut its emissions by more than 5 per cent, the cost would be upwards of $400 billion.

The ETS would raise $120 billion over 10 years if it cut emissions by the unconditional 5 per cent by 2020.

Following rumours the 2020 target could be lifted to 15 per cent or 25 per cent at Copenhagen, Mr Abbott made a simple linear multiplication to reach the $400 billion figure.

The Government said the real cost of an increased target would be about $150 billion and accused Mr Abbott of making a $250 billion blunder.

Campaigning in Townsville yesterday against the ''big whopping new tax'', Mr Abbott rejected he had got his figures wrong and accused the Government of having no modelling to underpin its claims. ''The Federal Government has never released the modelling,'' he said.

The Treasurer, Wayne Swan, said Mr Abbott was prone to making erratic claims. The assistant Climate Change Minister, Greg Combet, said Mr Abbott had ''demonstrated just how reckless he is and how unreliable he is''.

Mr Abbott claimed the Treasury figures had been ''superseded by events''. He alleged the Government had redone the work since ''and it's high time they released all this redone work''.

The Greens said Mr Abbott's misunderstanding of basic climate policy was ''astonishing'' but also blasted the Government, saying its defence exposed how cheap it would be to make more meaningful cuts to emissions.