BHP Billiton's Olympic Dam copper and uranium mine in South Australia will return to full operation by the end of June.

South Australian Premier Mike Rann said he had met with BHP Billiton chief executive Marius Kloppers and was told the news.

"After many many months of extraordinarily hard work by BHP Billiton and contractors ... BHP Billiton's Olympic Dam mine is heading back to full production," Rann told parliament.

Metal production at Olympic Dam was cut by 75 per cent after a shaft accident last October.

In a separate statement, Kloppers said that the development of BHP Billiton's Olympic Dam remains on track but is facing huge threat from the proposed resources super profits tax (RSPT).

"At the moment, it is not frozen," said Kloppers. "We are carrying on. We are spending money, there are 200 engineers working on it. Otherwise we would have made a statement to the contrary."

Kloppers, however, reiterated the mining company's stand against the RSPT, saying that the vast scale of the expansion was particularly threatened by the tax.

The Olympic Dam expansion was in the environmental impact statement phase and Kloppers said he would not be in a position to put a proposal to his board until late next year.

"Projects with enormous risks and very long lead times towards positive cash flows - because you're doing upfront investments for many years - are most disadvantaged by this type of tax being contemplated," said Kloppers.