In a staff note published overnight, IMF economists Michael Keen and Brendan Jones point to Australia as an example that ''highlights the political difficulties'' of limiting unwarranted free hand-outs to big polluters.

They said it was critical countries put a price on carbon, in the form of a tax or emissions trading scheme.

''Broader and deeper international carbon pricing must therefore remain a key priority in the coming years, with leadership by advanced countries essential to this process,'' they said.

The comments come just days after Mr Abbott, in his first act as Opposition Leader, dumped Coalition support for the Government's emissions trading scheme. He has promised neither an emissions trading scheme nor a carbon tax will be Coalition policy at next year's election.

Mr Abbott faces his first test as leader, and in particular of his decision to dump the emissions trading scheme, through today's by-elections in the blue-ribbon Liberal seats of Bradfield and Higgins.

The Greens are trying to make the by-elections a referendum on climate change and, with no Labor candidates running and after a fortnight of Opposition turmoil, are expected to provide a strong challenge to the Liberal candidates.

For more, pick up a copy of today's Canberra Times