SYDNEY - Australian Treasurer Wayne Swan on Sunday described as "myths" claims a planned new 40 percent tax on mining profits would hit investment or push up domestic prices.

In a weekly economic note, Swan said the new 40 percent Resource Super Profits tax would replace an inefficient royalties system and as a result, should boost investment.

Prices of most commodities subject to the tax were set on international markets, he said, and treasury analysis showed it should not affect prices of coal, gas or electricity within Australia.