Gina Rinehart has used a rare video appearance to repeat her warning that Australians need to work harder to compete with Africans who will labour for less than $2 a day.

In a reference to BHP Billiton's reasoning for shelving its Olympic Dam expansion plans, Mrs Rinehart says companies are "running a ruler" over their investments because of cost overruns and low productivity.

Yesterday, Fortescue Metals Group announced it was deferring some expansion projects and cutting costs, although its reasoning for the move was focused on a slump in iron ore prices rather that cost overruns.

Speaking in video posted on the Sydney Mining Club's website to discuss the recently signed enterprise migration agreement which will allow her to import 1,700 foreign workers for her Roy Hill Iron Ore project, Mrs Rinehart says Australians should not be complacent about the investment pipeline given that African labourers will work for less than $2 a day.

"Business as usual will not do, not when West African competitors can offer our biggest customers an average capital cost for a tonne of iron ore that's $100 under the price offered by an emerging producer in the Pilbara," she said.

"Furthermore, Africans want to work, and its workers are willing to work for less than $2 per day. Such statistics make me worry for this country's future."

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Listen Duration: 3 minutes 15 seconds 3 m 15 s Gina Rinehart lectures govt via YouTube ( Peter Ryan ) Download 1.5 MB

The comments come after Mrs Rinehart said last week that Australians need to work harder and socialise and drink less.

The fresh comments drew immediate criticism from the Prime Minister.

Julia Gillard says she does not agree Australia is a difficult place to invest and that she has a different view of how workers should be treated.

"It's not the Australian way to toss people a $2 gold coin and then ask them to work for a day," she said.

"We support proper Australian wages and decent working conditions for Australian people.

"We are not going to have wage rates the same as the wage rates in Africa. We're not going to compete on those kinds of cost differentials.

"We're going to compete on our great mineral deposits, our application of technology and high skills to the task. We mine differently than in other countries."

Special economic zone

In the video, Mrs Rinehart raised the idea of a "special economic zone" in northern Australia that would have lower taxes and fewer regulations to encourage investment.

"We need to create a large special economic zone in our north, stretching across northern Queensland, northern Western Australia and the Northern Territory, with fewer regulations and taxes, a region that truly welcomes investment and people," she said.

Mrs Rinehart also renewed her attack on the Treasurer Wayne Swan for what she calls a campaign of class warfare.

"Our federal and state governments must know that now, more than ever, we must lift our international competitiveness just to stay as well-off as we are," she said.

"And with state and federal debts, we must get realistic not just promote class warfare. Indeed, if we competed at the Olympic Games as sluggishly as we compete economically there would be an outcry."

Ms Gillard dismissed Mrs Rinehart's criticism as one driven by self-interest.

"We have a different view from Ms Rinehart about whether or not the mineral bounty in our natural landscape should be shared with all Australians or kept for the profits of a few," she responded.