In his first major speech as chief scientist, Professor Chubb said the climate debate in Australia ''borders on the appalling''.

''There are probably people now who think I am partisan because I'm saying the science is in on climate change. Well, I don't think that's partisan, I think that I can read English,'' he said.

''I think the evidence is overwhelming. Now there are respectable people who have a different view and … their different view should factor into what we do, but when you get the overwhelming majority of people with real expertise heading in one direction, you have to take notice of that because if you wait for proof you will wait forever … The experimental sciences don't do that. They gather evidence, critique it and do it again.''

The intervention by the two government advisers and renewed optimism about the carbon tax talks came as the Coalition leader Tony Abbott's proposal for a carbon tax plebiscite seemed doomed after the Family First senator Steve Fielding rejected the idea as a ''political stunt'' and an ''$80 million glorified opinion poll''.

Mr Abbott called Senator Fielding again last night to ''implore'' him to change his mind, but a spokesman for the senator had said there was ''absolutely no way'' that he would. Senator Fielding's vote would be needed for the idea to pass the Senate before it rises this week. When it next sits, the Greens, who oppose it, will have the balance of power.