Eco-activists and Aboriginal groups Tuesday condemned Australia's approval of a mammoth BHP Billiton mining pit expansion, warning of an environmental and public health disaster if it goes ahead.

Canberra on Monday green-lighted BHP's plans to extend its Olympic Dam uranium, copper and gold project in South Australia state, a move officials say could create the world's largest open-pit mine.

Expected to create thousands of jobs and boost exports, the Olympic Dam expansion was slapped with more than 100 environmental conditions to protect native species, groundwater and vegetation.

But environmental groups said the measures did not go far enough, with the left-leaning Greens party warning it would result in a "carcinogenic mountain range of radioactive waste".

"Instead of burying the radioactive tailings waste in a properly lined pit, BHP Billiton will dump 70 million tonnes of finely powdered radioactive tailings each year," said Greens Senator Scott Ludlam, describing the project as a "world's worst-practice uranium mine".

"The so-called environment conditions are hopeless -- there's no requirement for this tailing heap to be covered while the mine operates, and it is to operate for at least another 30 years," he added.

Ludlam said the mine would also generate at least 4.1 million tonnes of greenhouse gases every year, with four years of digging and billions of dollars of diesel fuel before BHP was even scheduled to hit the uranium ore body.

South Australia's Conservation Council said the expansion would have huge social, economic and environmental impacts, leaving "a legacy of radioactive waste, greenhouse emissions and the potential loss of iconic species."

BHP defended the mine, saying its approval followed "more than five years' work by hundreds of engineers, scientists, consultants and industry leaders across a broad range of expertise".

More than 4,000 submissions were received about the mine's potential impacts and a BHP spokeswoman said the miner was committed to "ensuring best practice in health, safety, environmental management and community engagement".

"We recognise the conditions laid out in the (approval) and the requirement to meet all of them across the life of the project," she told AFP.

On the radioactive waste issue, the spokeswoman said the expanded mine would build on technology and practices "that have been successfully implemented at Olympic Dam for 23 years".

"Seepage from the existing tailings facility has not resulted in any negative impact to people or the environment. This would remain the case for an expanded tailings system," she said.

But local Aboriginal elder and anti-nuclear campaigner Kevin Buzzacott said the mine was opposed from the outset because it was a sacred site for the area's Aborigines and they would not rest until the approval was reversed.

"We want BHP Billiton out of the desert," he said.

Once completed, the Olympic Dam pit is expected to be more than four kilometres long, 3.5 kilometres (2.17 miles) wide and one kilometre deep, with annual output of 750,000 tonnes of copper, 19,000 tonnes of uranium and 800,000 ounces of gold.