The MRRT, which taxes the profits of coal and iron ore companies operating in Australia, was initially slated to raise about $2 billion for the 2012/2013 financial year – and $10.6 billion over the next three.

However, that $2 billion target looks unreachable, with Treasurer Wayne Swan admitting today that MRRT revenues had taken a massive hit from the impact of continued global instability, volatile commodity prices and the high Aussie dollar.

The MRRT is a profits-based tax that yields revenue when the major miners are doing well.

“Revenues across the board are down very substantially,” Swan said.

He said the government had always supported transparency in its tax system and any revenue raised from the MRRT should be published.

The figures, the first batch of concrete numbers on the MRRT, come just a few months after mining tycoon Clive Palmer slammed the tax following reports it had yet to raise any money for the government.

The release of the figures caused a media frenzy today and gave the Coalition a free swipe at the Gillard government.

Shadow treasurer Joe Hockey hit out in front of the media, saying the MRRT had caused “enormous uncertainty for miners and investors.”

Hockey said that despite it being widely understood that the tax would raise little funds, this had not stopped the government spending “borrowed dollars.”

A huge industry backlash preceded and followed the tax’s implementation.

Palmer accused the MRRT of killing investment in Australia, while The Association of Mining and Exploration Companies labelled it “ill-conceived” and “poorly designed”

Western Australian Premier Colin Barnett even went so far as to label it “discriminatory”

While Rio Tinto has said previously it is not fazed by the MRRT, Fortescue Metals Group is a strong opponent.

The company is pushing to abolish it in the High Court of Australia, with a hearing scheduled for March.