He put the proposal yesterday because ''a first step is better than nothing''.

Greenpeace has also rejected the suggestion from Professor Flannery, chairman of the Copenhagen Climate Council.

Prime Minister Kevin Rudd wants the Senate to approve the Bill before the United Nations climate change conference in Copenhagen later this year.

Mr Rudd and Climate Change Minister Penny Wong will attend a summit next week called by United States President Barack Obama to speed up negotiations on climate change.

Mr Obama said the meeting would try to ''generate the political leadership necessary'' to achieve a successful outcome at the Copenhagen summit.

The US House of Representatives has narrowly passed a Bill to curb the greenhouse gases that scientists blame for global warming. (See separate story).

Professor Flannery said the low target in the Rudd Government's Bill would not limit emissions as much as he wanted.

''But we've got to start somewhere, unless we take the first step we're not going anywhere,'' he told the ABC. ''I personally think [the Greens] should vote for the [Bill] and get it through, because a first step is better than nothing.''