"The evidence is inarguable that Australia is becoming too expensive and too uncompetitive to do export-oriented business," Rinehart told the Sydney Mining Club in a rare public appearance. A video of her address was posted on the club's website.
"Africans want to work, and its workers are willing to work for less than $2 per day," she said in the video. "Such statistics make me worry for this country's future.
"We are becoming a high-cost and high-risk nation for investment."
Rinehart, whom Forbes estimated to be worth $18 billion in February, opposes a recently introduced mining tax as well as taxes on carbon emissions, which has created tensions with Gillard's government.
Rinehart has also called for miners to be allowed to bring in foreign workers, and her company Hancock Prospecting was granted government approval in May to hire just over 1,700 foreign construction workers for her Roy Hill project in Western Australia.
Gillard criticised Rinehart's remarks, saying the resources sector was doing well and had an investment pipeline of $500 billion, of which nearly half was at an advanced stage.
"It's not the Australian way to toss people $2, to toss them a gold coin, and then ask them to work for a day," Gillard told reporters. "We support proper Australian wages and decent working conditions."