But relations with the $50 billion coal industry appear to have hit a new low with the Australian Coal Association gathering funds for a multimillion-dollar anti-carbon tax advertising campaign after firing off an angry letter to the Climate Change Minister, Greg Combet, last week.

The letter dated May 18 from its chairman John Pelger said the figures that officials were using to calculate the cost of the carbon tax for coalminers were ''simply wrong'', that they were assuming the industry could use technology that did not exist ''at commercial scale anywhere'' and that unless the government changed its scheme the result would be ''job losses and mine closures''.

Officially the association says it is continuing to talk to the government, but sources said money was being collected to launch an anti-tax campaign.

As industry demands increased before an all-weekend meeting of the multi-party climate change committee seeking a final carbon tax deal, the government is examining an Australian Industry Group proposal for a ''third tier'' of assistance for high-emitting industries such as food processing, iron casting, plastics, chemicals and paper products, which would have missed out on assistance under the Rudd emissions trading scheme.

The government accepts it needs to do more to assist big-emitting manufacturers, already struggling with the high Australian dollar. The Opposition Leader, Tony Abbott, has targeted the sector in his anti-carbon tax campaign, saying it would ''kill'' manufacturing.

The government is holding separate talks to develop a package to assist the steel industry.

Support is also building for a multibillion-dollar fund to commercialise green technologies, with Professor Ross Garnaut - who delivers his advisory report to government next week - suggesting it should spend about $3 billion a year and a submission from the Australian Manufacturers Working Union asking for $3.6 billion over six years.

The union is proposing almost $7 million for manufacturing industry assistance.

Both are pushing for accelerated depreciation for companies that spend money on new energy-efficient plant and equipment and the AMWU is also demanding $1.5 billion in tax credits and other incentives for firms that make supply chains more energy efficient. The union says another $1 billion should be spent on the direct ''high-dollar'' compensation to companies, but only for the next two years.

The coal sector was offered $1.5 billion in compensation in the Rudd scheme, but Labor has refused to accept miners' argument that they should be eligible for full emission-intensive industry assistance because of the huge variation in emissions depending on coalmine geology.

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