Mineral sands producer Iluka Resources Ltd has joined the fight against federal government's proposed resource super profits tax (RSPT), urging its shareholders to contact local MPs.

Speaking during the company's annual general meeting in Perth, Iluka Resources chairman Bob Every stated, "While the company, in principle, would support the introduction of a well designed and structured resources tax, as a replacement for multiple State based royalties, this tax is nothing of the sort. It will instead add another layer of administrative compliance costs for companies. To call it a super profits tax when the hurdle rate applied is the risk free rate - the Commonwealth 10 Year Bond rate - is a misnomer and does not reflect the basis upon which resource companies make investment decisions."

Every said the planned super-profits tax, if implemented, "will make Australia less competitive, which must ultimately adversely affect the contribution of the resources sector to the national economy."

Iluka's managing director David Robb said initial analysis indicated the company would be sheltered from the impact of the planned tax scheme. However, he urged shareholders to consider the implications of the RSPT and write their local MPs about it.

Since it was announced, the proposed RSPT has been attacked by mining company executives and the federal opposition.

Iluka shares were down 7 cents, or 1.57 per cent, at $4.38 at 1457 AEST on Thursday.