A small salt miner in South Australian has appealed to the government, stating the resource super profits tax will not further help its firm as it is unviable.

The owners of Mugundawa Salt addressed a letter to Treasurer Wayne Swan and said the proposed 40 per cent tax would take half of the company's profits and also jeopardize employment in their 18 staff.

The firm explained that a small, regional mining firm should be excused from the tax.

Michael McNamara, Mugundawa's project manager, stressed the firm's risky situation as it will be forced to cut back its small mining operations or maybe consider closing it down.

“It is that severe because as we understand the tax could be applied to the whole of the operation and we've done some modelling that would suggest that the after-tax profit impact could be greater than 30 per cent - that is it'd reduce our net profit after tax by more than 30 per cent as it stands," Mr. McNamara sad.

"The tax is designed to be imposed on the cost of the commodity and the taxing point is at the mine site, so there's a potential that the rest of the value-adding that we do with our product could be caught up and taxed as the export miners are."

Earlier, Federal Liberal spokesperson Jamie Briggs expressed his concern on the effects of the proposed mining tax on smaller businesses.

"This is not just a great big new tax that affects BHP and Rio Tinto - it also affects small companies like this salt mine," Mr. Briggs said.

"What this means for this company is that any hope of expansion will be dashed, at the very least, under this great big new tax," he added.

However, a spokesperson for Mr. Swan said the company will be subjected to review, and adds that low-value commodities such as salt are also included in the discussions on the mining tax.