Fortescue Metals Group chair Andrew Forrest said on Tuesday that the federal government would be better off should it decided to completely dump the proposed mining resource rent tax as it would only benefit Xstrata, BHP Billiton and Rio Tinto, three of Australia's largest mining firm.

Mr Forrest said that the current form of the mining tax would not stay for long as he believes that the government would opt for another revision should its present coverage of iron ore and coal only proved unprofitable in the long run.

The mining magnate also told his Diggers and Dealers forum audience that the government erred when it decided to exclude magnetite ore as among the minerals to be exempted by the new tax measures.

Mr Forrest added his voice to the mining industry's resurging criticism on MRRT with forum chairman Brian Eldridge even mocking the proposed tax as nothing but plain economic terrorism, warning that the tax would surely see revisions once the Labour party managed to retain government power.

However, Foreign Affairs Minister Stephen Smith maintained that the scathing remarks made by Mr Eldridge on a mainly economic issue only proved the revived campaign against the mining tax is being motivated by political interests.

Mr Smith cited that during Mr Eldridge talks, he took a partisan stand by encouraging the Diggers and Dealers delegates to junk the Labour party in favour of candidates from the Liberal group.

On another front, the Association of Mining and Exploration Companies (AMEC) had revived its ad campaigns in opposition of the mining tax last week as association head Simon Bennison underscored that the ads were restarted to voice out the majority of the industry's opposition to MRRT.

Mr Bennison said that the campaign's focal issue is AMEC's stand that the government must give equal priorities to all Australian mining companies as he enjoined all industry players to join the fight against the tax measure, which he said has been opposed by his group from day one.

He also re-echoed the mining industry's general sentiments that the MRRT would eventually saw major amendments.