Prime Minister Kevin Rudd says threats are standard from mining companies, which are accused of "crying wolf" with claims a planned resources tax puts their projects in peril.
Resource companies are furious about the plan, with one of them, Origin Energy, claiming the tax jeopardises a $35 billion liquefied natural gas project in central Queensland.
But Rio Tinto has denied reports it was considering shelving plans to spend $11 billion on expanding its iron ore operations in Western Australia due to the tax, announced on Sunday.
Mr Rudd on Thursday said it would create a fairer system - with $1 in every $3 of mining profits returned to the Australian people through taxes, instead of $1 in $7 as it is now.
He welcomed the support of former Reserve Bank boss Bernie Fraser, who has backed the proposal as "very much in the national interest". "Inevitably, (Mr Fraser) said, there's going to be some crying wolf in all of this," Mr Rudd told reporters in Victoria.
"So I imagine that some within the mining industry will dig deep within their very deep pockets and seek to run a political campaign."
The government would not be deterred "one bit" and threats and warnings of project closures were inevitable.
"That's the way in which negotiations with mining companies usually happen," Mr Rudd said.
The opposition has confirmed it will vote against the 40 per cent tax on mining profits if Labor wins the next federal election.
Finance spokesman Andrew Robb said his party would "absolutely" vote against the tax, but believed it was such a bad plan, it would be scrapped before then.
"This will be exposed for what it is," he told ABC Radio on Thursday.
"This is going to blow up in the prime minister's face."
But Mr Rudd said Opposition Leader Tony Abbott should think carefully, as blocking the tax would stop a superannuation changes flowing to workers, and tax breaks benefiting businesses.
"If Mr Abbott blocks these reforms he's standing in the way of, and blocking, better super for working Australians for their retirement and decent tax breaks for 2.4 million Australian businesses," he said.
