INDEPENDENT Senator Nick Xenophon will back the Coalition to repeal the carbon tax if it wins government at the next election.
Opposition Leader Tony Abbott has repeatedly emphasised his plans to repeal the carbon tax if he becomes Prime Minister.
But Senator Xenophon, who spoke on Sky News on Sunday, said he would only help if a viable alternative for reducing Australia's carbon emissions was put forward.
"You need to have an alternative in place because both the government and the coalition (have) committed to a reduction in carbon emissions by 2020," he said.
"The question is we need to have a sensible, robust debate in this country.
"What is the most effective way of reducing emissions, in economic terms, in terms of getting your best environmental bang for your buck?"
In less than six weeks, about 500 of the nation's biggest polluters will be forced to pay $23 for every tonne of their carbon emissions.
A list released about two weeks ago showed many of the firms taxed will be in the mining and resource industries, as well as local councils, with a high number of companies operating in Queensland.