He said that it would be up to them to consider any future changes to the tax ''given the fact that it has not collected any real revenue of any significance so far''. ''I'll leave it with them,'' he told Sky News, while emphasising that he did not know what undertakings Ms Gillard and Mr Swan had given the mining industry when they renegotiated the tax in 2010. The tax was first proposed when Mr Rudd was prime minister - coming out of the Henry Tax Review - but negotiations broke down with the mining industry. When Ms Gillard became Prime Minister in mid-2010, she made renegotiating the mining tax one of her top priorities, but it has since been argued that the tax was watered down in the process. It was forecast to raise $2 billion in the 2012-13, but last week Mr Swan revealed that it had only raised $126 million in the first two quarters, sparking a renewed push by the Greens and independents and some within Labor to restructure the tax.

Some Labor MPs, such has Labor Left leader Doug Cameron, have been backing Labor to have a new ''stoush'' with the mining industry, despite the damage this might do in an election year.

Mr Rudd appeared to agree with that approach. ''No government should ever take a backwards step in pursuit of the national interest,'' he said. Environment Minister Tony Burke said that Mr Rudd's contribution to the mining tax debate was not ''necessarily unhelpful''. ''He was obviously there right in the centre when the mining tax was first proposed,'' Mr Burke told Sky News on Tuesday afternoon. Mr Burke said that taxes got reviewed from time to time but there were ''no plans'' to change the mining tax ''at the moment''.

The Coalition continued to focus on the mining tax during question time, using almost every question they had to grill the government on whether it would change the design. Greens MP Adam Bandt, also asked Ms Gillard if she would close the royalties loophole before the May budget. Ms Gillard told Parliament: "The government has no plans to change the design of the MRRT." When Opposition Leader Tony Abbott asked the Prime Minister to rule out any further changes to the tax "yes or no", Ms Gillard repeated her statement that the government had "no plans" to alter the tax. Mr Rudd, the member for Griffith, is maintaining a public profile as the government heads towards the polls on September 14 and predicted that the year would be ''tough, ugly and bloody''. He said that Labor could win the election but did not specify that it would be under Ms Gillard.

''Of course the Australian Labor Government can win and can win under the Prime Minister's leadership.'' This comes as two Labor backbenchers, Stephen Jones and Joel Fitzgibbon, said that the royalties arrangement with the states was unsustainable into the future. Follow the National Times on Twitter