The policy exceeds the forecasted 35 per cent reduction put forward by Prime Minister Scott Morrison at the Glasgow summit last month.
The policy is expected to be announced later today.
Speaking on Today this morning, Labor Deputy Leader Richard Marles was pressed on the details.
“We will be articulating a very clear path to how we get to zero net emissions by 2050 – because we actually believe in it,” he said.
“And that stands in stark contrast to the government who really have a pretty hollow policy around all of this.”
Coalition frontbencher Peter Dutton called Mr Marles’ comments “complete nonsense”.
“We’ve reduced emissions by 20 per cent,” he said.
“We’ve got the biggest investment into renewable energies in the world – the solar uptake is as high as anywhere in the world.”
The Greens, meanwhile, have proposed a 75 per cent reduction by 2030 and net zero by 2035.