The federal opposition called on the government to ascertain that taxpayers would not foot the bill of cleaning up an environmental mishap such as the Gulf of Mexico oil spill once the controversial resources super profits tax is implemented.

Opposition environment spokesman Greg Hunt noted that the proposed tax carries a guarantee of up to 40 percent government paybacks to a company in the event of project failures, which could also mean that taxpayers would be burdened should an environmental disaster occurs.

He said that such measures were geared to discreetly nationalise resources companies and any attending disasters by default, when the case should be that "companies are responsible for the costs of any environmental disaster, and that being the principle around the world."

For his part, Environment Minister Peter Garret said that it is premature to say that taxpayers would be liable for any clean-up costs of a disaster as the exact details of the super profits tax have yet to be determined or even finalised.

He added that more details would be discussed and worked through during planned negotiations as he gave assurance that "we set the bar very high here for environment standards as we are very aware of the fact that the environment needs to be protected."

In a related development, Finance Minister Lindsay Tanner gave hints that changes could be considered and adopted in the manner that existing mine sites and projects should be regarded under the new tax measures.

He acknowledged that raging debates on the super profits tax have been largely sparked by "how existing mines are treated and, in effect, the valuation methodology that's used," as he added that a lot of sound arguments are being absorbed by the government as legitimate points of negotiations.

Prime Minister Kevin Rudd is set to speak in Perth today amidst threats of protests coming from segments of the mining sector opposed to the planned super tax as Mr Rudd gave assurance that discussions with the mining industry are underway but kept mum on concessions that the government is willing to give to miners.