Former prime minister Kevin Rudd says the mining tax has not collected "any real revenue of any significance", as the government faces pressure to amend its design.
Crossbench MPs are urging the federal government to close loopholes in the minerals resource rent tax (MRRT) including offsetting state royalties mining companies pay against their MRRT liabilities.
But the coalition says the tax, which raised only $126 million in its first six months of operation, should be scrapped as it damages business confidence.
Mr Rudd, who lost the Labor leadership in 2010 partly because he could not deliver the previous version of the mining tax, said any further changes were in the hands of Treasurer Wayne Swan and Prime Minister Julia Gillard.
He attributed the format of the original mining tax to Mr Swan, who he said had "brought it to the relevant ministers of the government, including the then deputy prime minister (Ms Gillard) and myself".
"I think in terms of any future changes to the tax, given the fact that it hasn't collected any real revenue of any significance so far, that really is a matter for the prime minister and for the treasurer to consider and I will leave it with them," Mr Rudd told Sky News.t
He said he was "unfamiliar" with the undertakings given to mining companies by Ms Gillard and Mr Swan when they negotiated the MRRT, but any changes would need to be mindful of these.
"My view has always been pretty basic," Mr Rudd said.
"These resources are owned by the Australian people ... (and) I believe the Australian people deserve, through an appropriate tax mix, an appropriate return.
"No government should ever take a backward step in pursuit of the national interest."
Ms Gillard on Monday told parliament the current GST distribution review, which is the subject of talks with the states, also was considering the issue of refunding state mining royalties.
Shadow treasurer Joe Hockey says the government should show a "little bit of ticker" and be honest with the Australian people about any changes to its mining tax.
Assistant Treasurer David Bradbury ruled out any change to the MRRT, saying the government will continue to monitor the revenue receipts "as and when they come in".
"This is a very volatile tax ... resource rent taxes always are," he told reporters in Canberra.
The government also would address any budgetary implications in the May budget, he said.
Independent MP Tony Windsor said the issue between royalties and the MRRT rent must be addressed.
"If there is structural issues, let's fix them," he told reporters.
"If it's only profit issues, well leave it alone."
Independent MP Rob Oakeshott, who backed the MRRT in the parliament, says the government told him that hiked state government royalties would not be offset against the tax.
When asked whether he felt duped by the government, Mr Oakeshott told ABC Radio on Tuesday: "Partly ... yes a bit duped".
The NSW MP said he had a letter from the government indicating its willingness to implement a recommendation from the Henry tax review to replace state mining royalties with a rent resource tax.
"They recognised royalties are unsustainable and a bad tax for Australia and a better way forward is with a national resource rent tax."
Mr Oakeshott has seconded an Australian Greens bill that closes that loophole.