FIFTY companies were responsible for half of Australia's greenhouse gas emissions and would pay the bulk of the carbon tax revenue, the Climate Change Minister, Greg Combet, said yesterday.

In a speech to the National Press Club in Canberra, Mr Combet said about 1000 companies would pay the tax on carbon but only a small number would be the main contributors.

''The latest … data shows that the 50 largest polluters account for over 50 per cent of Australia's carbon pollution,'' he said.

''When you include sectors that will not be covered by the carbon price, the 50 largest polluters will be responsible for around two-thirds of carbon liabilities.''

The climate change department's website says the top five emitters are Macquarie Generation, Delta Electricity, Great Energy Alliance, International Power and CS Energy.

Next are TRUenergy, Eraring Energy, BlueScope Steel, Loy Yang and OzGen. Other companies in the top 50 include Woodside, Rio Tinto, BHP, Qantas, and Xstrata.

Mr Combet also sought to play down a carbon price's impact on heavy industries such as aluminium and steel.

Heavy industry accuses the government of preparing its compensation deal based on what was proposed under the dumped emissions trading scheme, which they say is outdated.

But Mr Combet said under the 2009 scheme a $20 carbon price, after 94.5 per cent free permits for the industry, would have only raised the cost of making steel $2.60 per tonne, out of a market price of $800 a tonne. For aluminum, it would cost $18.70 out of a market price of $2500.

But the Australian Aluminium Council executive director, Miles Prosser, said Mr Combet's estimates did not include electricity costs, domestic gas costs and any caps or constraints on permit allocation to industry.

Mr Combet committed the government to returning more than 50 per cent of the carbon tax revenue to households.

The Opposition Leader, Tony Abbott, said Australians could not trust the government.

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