Newcrest Mining chief executive Ian Smith says the federal government's proposed tax on miners could cost his company 5 per cent in net present value.
But Mr Smith also said that was the worst case, and he expected that the proposed tax was unlikely to be passed without changes.
"If you take an average expectation of prices at the worst case scenario it has an overall NPV effect on us of around five per cent," he said in a briefing today, after Newcrest announced it had agreed to takeover rival Lihir Gold.
"If there was to be some changes to the configuration of the legislation ... the expectation is that number would come down.
"The expectation of this going through parliament in its present configuration, if you want to put a probability on it, I would put it at a fairly low number."
On Sunday, the government announced its response to the Henry tax review, which will involve imposing a 40 per cent tax on profits made from non-renewable resources from July 1, 2012.
The announcement prompted a flurry of angry responses from miners and lobby groups, which say the tax grab would discourage investment in Australia and possibly cost jobs and affect the wealth of Australians.
The tax increase proposal also affected the market value of resource companies with investors yesterday fleeing stocks that held projects in Australia. The activity wiped more than $8 billion off the value of Australia's main resources index.
