PM, treasurer designed flawed tax: Libs - The Australian

The opposition says the PM and the treasurer are to blame for the shortfall in mining tax revenue. Source: AAP

THE federal opposition says the Prime Minister Julia Gillard and Treasurer Wayne Swan are to blame for a substantial shortfall in mining tax revenue.

To the end of December the minerals resource rent tax garnered only $126 million, making it almost impossible for the government to reach its revenue forecast of $2 billion by the end of June.

The government attributes the shortfall to a drop on iron ore and coal prices, but The Australian reports that much larger-than-expected mining tax deductions are to blame.

The opposition's junior treasury spokesman Mathias Cormann says the prime minister and treasurer should take the blame for negotiating the design of the tax with the three big miners, BHP Billiton, Rio Tinto and Xstrata.

"As well as excluding any other mining industry stakeholders and state governments, they also, extraordinarily, excluded all Commonwealth officials from that negotiating process," he said in a statement on Monday.

"The coalition has said for some time that Labor's MRRT was a fiscal train wreck in the making."

Mr Swan overestimated the gross revenue from the MRRT and underestimated the cost of the various concessions he and Ms Gillard made in their heads of agreement with the miners, Senator Cormann said.

The government wanted the MRRT to fund an increase in the superannuation guarantee levy from nine per cent to 12 per cent, removal of the 15 per cent superannuation contributions tax for low-income earners and instant asset write-offs of up to $6500 for small businesses.

Cabinet minister Bill Shorten says the superannuation measures will be funded from consolidated revenue.

"We'll pay for this tax that we've cut and the Liberals want to reintroduce," he told ABC radio, adding 3.6 million Australians would be paying more under a coalition government.

"Not even the Sheriff of Nottingham could've dreamed that up."

Labor senator Doug Cameron says the tax base needed broadening because Australia had one of the lowest in the world.

"You can't have Scandinavian-type benefits for the population with Bangladesh tax rates," he told reporters in Canberra.

"If there's any stoush between now and the next election it should be with the miners to give the Australian community a fair go."

Australian Greens deputy leader Adam Bandt described the mining tax as a "dud".

"It's clear the big miners got the upper hand in the backroom negotiations," he told reporters in Canberra.

The MP warned if the mining tax was not beefed up before the federal budget, there would be severe spending cuts.

Mr Bandt will introduce a private member's bill in the lower house on Monday that aims to close a loophole in the mining tax that will stop the Commonwealth having to reimburse miners if state governments hike royalties.

"It's time Labor admitted it made a mistake," he said.

Cabinet minister Craig Emerson said the mining tax was designed to be flexible.

"We don't have any plans to change the design of the tax," he told reporters.

"The coalition complains when it's not collecting revenue, they complain when it is collecting revenue."

Claims the mining tax revenue wouldn't cover administration costs were false, Dr Emerson said.