In Parliament, ousted Opposition Leader Malcolm Turnbull pledged to cross the floor and support the Government's emissions trading scheme. He criticised Mr Abbott's ''direct action plan'', which included a $1 billion fund to subsidise business and industry projects to reduce emissions.

Mr Turnbull said the emissions trading scheme was the only credible way to meet the target a 5 per cent reduction in emissions by 2020.

An alternative strategy which involved using taxpayers' money to subsidise projects to reduce emissions would prove more costly and ''achieve very little''.

''All of us know ... that industry and businesses attended by an army of lobbyists are particularly persuasive and all too effective at getting their sticky fingers into the taxpayer's pocket,'' Mr Turnbull said as Liberal colleagues Joe Hockey, Petro Georgiou and Russell Broadbent looked on.

''Having the government pick projects for subsidy is a recipe for fiscal recklessness on a grand scale and there will always be a temptation for projects to be selected for their political appeal.

''In short, having the government pay for emissions abatement as opposed to the polluters themselves is a slippery slope which can only result in higher taxes and more costly and less abatement of emissions.''

Mr Abbott ''respected'' Mr Turnbull's right to cross the floor saying, ''Unlike the Labor Party we're not Stalinist.''

The Government called Mr Turnbull's speech ''courageous'' as polls indicated voter support for its emissions trading scheme was waning.

For more on Federal politics, see today's Canberra Times.