Sydney  - Australia's opposition Liberal Party leader Malcolm Turnbull delivered an ultimatum Thursday to climate-change sceptics within his party.

He threatened to quit as leader unless they joined him in endorsing the emissions-trading scheme that the ruling Labor Party is pledged to introduce in July 2011.

"I will not lead a party that's not as committed to effective action on climate change as I am," Turnbull told reporters. "Anyone who thinks it's electorally wise to have a do-nothing-on-climate-change policy is not in tune with the mood of the nation, or the mood of the globe, frankly."

Prime Minister Kevin Rudd has pushed legislation through the lower house, where Labor has a majority, but the bill to bring in a cap-and-trade emissions scheme has been blocked in the upper house, where the balance of power is held by minor parties.

Turnbull, who was environment minister in the previous Liberal-led government, has promised to negotiate a compromise with the government that would allow the bill to go through.

"Our policy has always been to take effective action on climate change," he said. "I'm sending a message to every Australian that Malcolm Turnbull is committed to action on climate change."

The opposition, which includes the Liberal Party's coalition partner the Nationals, is split on efforts to curb the greenhouses gases that cause climate change.

Some are out-and-out climate sceptics and are opposed to any abatement measures while others argued that Australia should let other countries do the heavy lifting on curbing climate change.

The Liberals endorsed a carbon-trading scheme when John Howard was prime minister but have bickered about the proposal since being turfed into the opposition in the November 2007 election, which brought Rudd to office.

"If we simply say we don't like the government's emissions-trading scheme but are not prepared to say why we don't like it and what changes we would demand to make it satisfactory, then we can reasonably be described as being a party of no ideas," Turnbull said.

One of the leading rebels, Nationals member Barnaby Joyce, said he would not bow to pressure on the issue.

"The Nationals have been consistent, and we do not believe an emissions-trading scheme is a good idea - it's a massive tax that will have no effect," Joyce said.

Australia is among the world's biggest polluters on a per-capita basis with emissions per head at least five times China's. It's the world's largest exporter of coal, the emissions-rich, non-renewable energy source it relies on for more than 80 per cent of its power generation.

Rudd has promised a unilateral reduction of 5 per cent by 2020 in emissions from 2000 levels. He said lifting the target above 5 per cent would be possible if other countries, including developing nations, also set targets in that range at the United Nations-sponsored meeting in Copenhagen at the end of the year. (dpa)