It also fuelled speculation of an internal push to damage Mr Shorten, whose approval ratings have recently plummeted, and who has fought to contain the fallout following his appearance at the trade union royal commission. Labor's environment spokesman Mark Butler has called the latest figures a disgrace. Credit:Alex Ellinghausen News Corp reported on Wednesday that Labor had drafted new plans for a carbon tax ahead of its national conference later this month. Mr Shorten dismissed as "complete rubbish" reports that his party was planning to resurrect the controversial policy. Labor environment spokesman Mark Butler said the party had long pledged to go to the election with an emissions trading scheme that placed a legal cap on carbon pollution, similar to that operating in the US, parts of Europe, South Korea and China.

The options also reportedly include emission standards for cars, new laws for power plants, energy efficiency targets and a plan to phase out coal for renewable energy. Prime Minister Tony Abbott said Labor "wants to damage our economy by reintroducing … a triple whammy carbon tax on households, on power stations and on cars". Environment Minister Greg Hunt said the leak revealed a split in Labor "of catastrophic proportions ... was it a plan to kill the tax or kill Bill?" Three members of shadow cabinet told Fairfax Media they did not know if the document had been leaked to damage Mr Shorten, or to pull back on the scope of Labor's climate policy. All three expressed strong support for Mr Shorten and said a range of theories were being discussed internally about the source of the leak, including that the proposal may have been left at a Commonwealth parliamentary office and found by a government staff member.

"I just don't see who benefits from this; there is no obvious culprit" one shadow minister said, "and the irony is that the policy has broad support". That MP said the party would not shift, nor water down its position as a result of the leak. A second shadow cabinet minister conceded the leak may well have been designed to damage Mr Shorten but said "this can't and won't blow us off course" on climate policy, and that the Opposition Leader's position was not threatened. It is understood the document had gone through a number of iterations and was tightly held, having been seen by no more 20 MPs and staffers, though aspects of it had been discussed with stakeholders including economists, business groups and green groups. Other Labor frontbenchers said there was little dispute in shadow cabinet about the decision to embrace emissions trading as part of the party's election platform.

That decision had been largely settled shortly after the 2013 election loss and several documents canvassing how this might look have since been drawn up, with input from key players including Mr Butler, former climate change minister Greg Combet, Mr Shorten and ALP national president George Wright. However, shadow cabinet has not yet decided what form of emissions trading Labor should adopt. Options being canvassed include a "cap and trade" scheme such as in Europe, or amending and toughening parts of the Abbott government's Direct Action plan to ultimately turn it into a form of trading scheme. One senior Labor source said there was wide recognition that the ALP would have to fight off another anti-carbon tax campaign when its policy is launched, meaning it would have to successfully explain to voters that a tax is not an emissions trading scheme. With Judith Ireland Follow us on Twitter