Greens leader Richard Di Natale says a massive audit should be undertaken across the country to work out whether state governments have the money to cover mine rehabilitation.

Australia is currently home to about 50,000 abandoned mines, left to sink into the ground at a time when companies could simply walk away if their profits dried up.

The mitigation of dangerous effects of these mines falls to the state and territory governments, but Senator Di Natale is worried that they do not have the financial bonds to properly rehabilitate them.

Given the extraordinarily un-environmentally-friendly mining practices of yesteryear, it is a heavy burden for the states to bear.

“We need to conduct a national audit that tells us exactly what those liabilities are to ensure that we know exactly what amount of money needs to be spent to rehabilitate mines once they are closed,” he said.

Senator Di Natale said the rate of mine closure would only increase as the world moves away from coal.

“The rapid decline in Australia's coal exports in recent years is not a cyclical blip but a structural and terminal decline that will not recover,” he said.

Media investigations suggest that in NSW alone, there are more inactive coal mines than active ones.

Reports say there are 46 coal mines in operation right now, while 55 have been placed in “care and maintenance”, which means they are not operating but not yet retired.

Around 55 coal mines have been entirely abandoned.

Experts have told reporters that the actual cost of rehabilitation could be as anywhere from three to 10 times more than the amount states currently hold in bonds.

Executive director of coal at the Minerals Council of Australia – the top resource industry lobby – said Senator Di Natale was engaging in “activism fiction”.

“I think on the whole Australians are very well satisfied [with] the way the mine industry is a responsible industry, a tremendous employer, pays taxes, pays royalties and is highly regulated with the most stringent environmental conditions in the world,” he said.

“If you look at the numbers from reputable sources such as the International Energy Agency, and indeed our own forecast, you see that Australia will be the largest coal exporter in 2017.

“This is merely an attempt by the Greens to try and damage a great industry, the Australian coal industry.”