Divisions also emerged yesterday in the union movement, as the Australian Workers Union criticised the ACTU, which — while backing the Government's plan — has urged it to keep open the possibility of a tougher target and invest in a "green new deal".

The AWU, strongly supporting the Government's scheme and highly critical of the Greens, said it would approach the Coalition to get the scheme through the Senate.

Prime Minister Kevin Rudd, in Kununurra, WA, to publicise the Government's provision of $195 million to help expand Ord agricultural production, rejected criticism that the emission scheme's targets were too modest.

Given the global financial crisis, the Government "makes no apologies whatsoever for introducing responsible medium-term targets", he said.

As Greens, Opposition, Family First and independent Nick Xenophon agree on one thing — the need for a Senate inquiry — Nationals leader Warren Truss said the scheme's complexity "would make it a nightmare".

It would "just export emissions and Australian jobs", he said, and would hit some of the nation's most energy-efficient transport sectors with much higher energy taxes.

Senate Nationals leader Barnaby Joyce said the Senate inquiry should be carried out by the economics committee, rather than the environment committee.

Although he would not say the emissions scheme should be opposed in the Senate, he said that "at first blush" there were serious concerns.

But Opposition environment spokesman Greg Hunt and climate change spokesman Andrew Robb were non-committal.

Mr Hunt said the Coalition would have a response in February, after it received the results of an assessment it has commissioned.

"We won't be rushed in the meantime into endorsing, opposing or suggesting amendments," he said.