Labor leader Bill Shorten has distanced himself from remarks made by opposition environment spokesman Mark Butler who said the case has been made for Australia to cut its greenhouse gas emissions by 15 per cent by 2020.
Mr Butler said the conditions for Australia to lift its emissions target from a minimum of a 5 per cent cut to 15 per cent by 2020 had been met, based on an assessment of what other countries were doing to tackle climate change.
Campaigning in Perth before the West Australian Senate election on Saturday, Prime Minister Tony Abbott seized on Mr Butler's remarks, arguing they were a sign Labor was not just going to keep the carbon tax, but increase it.
Mr Butler's comments came as the UN's Intergovernmental Panel on Climate Change warned of irreversible global warming damage due to the high level of global emissions and followed a Labor-led Senate committee last week calling for deeper cuts. It demonstrates the Labor Left faction leader's preparedness to take on the hard-heads in the Labor Right over emissions targets.
Australia's current policy is for an unconditional 5 per cent reduction in emissions by 2020 against 2000 levels, but with room to move to a target of 15 per cent to 25 per cent depending on global action.
The independent Climate Change Authority, which the government plans to abolish, said in February Australia should adopt a minimum target of 15 per cent by 2020 and its 5 per cent target was out of step with countries including China and the United States.
Mr Butler said: ''It [the authority report] does make the point that the conditions for 15 per cent have been met.
''For example, similar countries have targets of 15 per cent. It's quite clear 20 per cent hasn't been met but it is strongly arguable 15 per cent has been met.'' A spokesman for Mr Shorten said the climate authority had said a 15 per cent reduction in emissions was achievable with the right policy settings.
But he added: ''Labor isn't going to be announcing 2020 targets from opposition in 2014 - who knows where we will be come 2016 under an Abbott government, which has no plan to reduce emissions.''
Other Labor MPs closed ranks on Tuesday. Several frontbenchers declined to comment on Mr Butler's remarks.
In opening remarks at a cabinet meeting in Perth, Mr Abbott said Mr Butler's comments showed Labor planned to ''not only keep the carbon tax but increase it''.
They're going to need an even bigger carbon tax to try to achieve that reduction.
''If they're going to raise the emissions reduction target from 5 per cent to 15 per cent, obviously they're going to need an even bigger carbon tax to try to achieve that reduction,'' he said.
This conflicts with the advice of the Climate Change Authority, which found the carbon price would not be materially affected by increasing the target if - as under the current legislation - Australia's carbon market was linked to international markets from 2015.
Mr Butler's comments are not a formal shift in the party's policy settings, but show he intends to fight for the party to lock in an emissions reduction target of 15 per cent by 2020.