The nation's biggest miners are descending on Canberra today armed with new ammunition in their fight against the mining profits tax.
The Minerals Council is holding a two-day conference in Canberra, which coincides with the release of a new study on the profits tax.
The council's spokesman, Mitch Hooke, says the report by accounting firm KPMG shows gold and copper mines will not be viable under the new tax, while the net present value of new coal mines will be more than halved.
"They will either be deferred, shelved, or just simply cut," he said.
Mr Hooke says investment will move offshore.
"The international investment community is saying, 'what are you doing, do you understand the ramifications of what you are doing - not just for your industry but for this country as a whole'," he said.
Rio Tinto says the KPMG report found it paid an effective tax rate of 35 per cent, amounting to more than $20 billion, over the past 10 years.
The figures challenge the Federal Government's claim that resource companies pay on average a tax rate of 17 per cent.
Rio Tinto also says the $37 billion it has made over the past decade in profits after tax has been re-invested in Australia
But Treasurer Wayne Swan says the miners cannot be believed.
"What we have is a grievous misrepresentation of what the Government is doing," he said.
Mr Swan says the mining industry's campaign against the tax justifies the Government's decision to do its own advertising.
"We are running a factual campaign. It goes to the core of our plans for the future to modernise, to strengthen our economy by modernising the tax system," he said.
"What we are doing is putting the proposals out there clearly because the have been grossly misrepresented by vested interests who stand to benefit.
"I couldn't think of anything more important for a Government to do than clear up those misrepresentations."
But the Federal Opposition said it was clear the Government was planning a mining tax advertising campaign well before the proposed tax was announced.
The Government has repeatedly said the campaign is needed because the mining industry is spreading misinformation about the new tax.
But a Treasury official has confirmed the Government began doing market research in March and had prepared an advertising campaign by April - before the tax was announced in May.
Liberal Senator Michael Ronaldson says the Prime Minister has been caught out.
"This puts paid to the public line being run by the Prime Minister and the Treasurer," he said.
"Clearly, what is happening is that the great big new tax on mining - and the advertising of it - was in place well before the mining industry got involved."
Prime Minister Kevin Rudd is skipping the miners' conference, but Opposition Leader Tony Abbott will give a lunchtime address.