Opposition environment spokesman Mark Butler says the case has been made for Australia to reduce its emissions by 15 per cent by 2020, in the clearest signal yet of the ALP's policy direction on climate change.
Mr Butler's comments come a week after a senate committee called for deeper cuts in emissions, as the IPCC warned of irreversible global warming damage, and demonstrate 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.
In his strongest comments about emissions policy since the election, Mr Butler told Fairfax on Monday "it is strongly arguable" that the requirements for setting a target of 15 per cent have been met.
The independent Climate Change Authority (CCA), which the government is abolishing, said in February that Australia should adopt a minimum target of 15 per cent by 2020 and that Australia's current 5 per cent target was out of step with countries including China and the US, who were setting more ambitious targets.
"It [the CCA report] does make the point that the conditions for 15 per cent have been met," Mr Butler said.
"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."
Mr Butler's comments are not a formal shift in the party's policy settings but demonstrate Mr Butler intends to fight internally for the party to lock in an emissions reduction target of 15 per cent by 2020.
During last year's leadership contest Labor's Left faction was concerned about now-opposition leader Bill Shorten's commitment to pricing carbon.
Since the election, the Abbott government has stuck with a 5 per cent target, which it says it will review next year.
Two weeks ago Mr Shorten gave a strongly worded speech in which he lashed climate change conspiracy theorists, keyboard warriors and social media trolls for hijacking the debate about man-made climate change.
A carbon price is an article of faith for the Labor Left, but there are sections of the ALP's Right faction who fear going to the 2016 election promising a price on carbon emissions.
Labor has voted against the Abbott government's carbon tax repeal.
Labor's policy is to move to an emissions trading scheme from July, one year sooner than legislated.
Speaking after the publication on Monday of a major assessment by the UN Intergovernmental Panel on Climate Change, Mr Butler said it was important to "have strong individual voices in what is a diabolically complex area of policy".
"That's why we're opposing the abolition of the (Climate Change) Authority," he said.
He said it was the government's statutory responsibility to respond to the CCA's recommendations.
"At the end of the day we are not the government," he said.
"They are the ones who have a statutory responsibility to respond to this."