Labor's proposed action on climate won't cost the economy but will help it grow in the next decade, according to Bill Shorten.
The coalition, however, says the opposition leader's claim is "evasive and misleading".
A day after refusing to answer questions on how much Labor's climate and energy policies would cost, Mr Shorten on Wednesday pointed to findings by ANU economist Warwick McKibbin.
The opposition has vowed to introduce a target to reduce carbon emissions by 45 per cent by 2030, compared to 2005 levels.
The coalition has an emissions reduction target of 26 per cent.
Mr Shorten maintains that under both targets, Dr McKibbin's modelling shows Australia's economy would continue to grow, racking up growth of 23 per cent throughout the 2020s.
He argues the finding means the policies aren't a cost.
"Our economy is going to grow, I don't accept the characterisation that it's a cost," he told reporters in Perth on Wednesday.
"We are going to grow because we are going to move to a lower carbon pollution economy and there's other aspects which means that we will grow, but the modelling has been done."
But senior coalition minister Simon Birmingham says Mr Shorten's comments about Dr McKibbin's modelling are misleading, as the economist was clear his work "did not examine Labor policy".
He pointed to modelling by climate change adviser Brian Fisher of BAEconomics, which found Labor's emissions reduction target will cost $472 billion by 2030.
"Growth will be slower. That means fewer jobs, lower wages, for Australians under Labor's policy," Senator Birmingham told reporters in Canberra.
Dr McKibbin has called Dr Fisher's work "highly credible", the senator noted.
Mr Shorten earlier stressed it would be expensive not to address the changing climate, given natural disasters cost Australia $18 billion each year.
"There is a cost of not taking action," he told ABC Radio Perth.
Not having a clear energy plan has also driven up power prices across Australia and prevented investment in power generation, he said.
Mr Shorten said Labor would allow companies to purchase offsets if they can't meet their emission reduction targets through productivity changes.
But he doesn't expect the cost to companies of needing to buy the offsets would be near $472 billion.
"I don't accept that the price of buying international offsets is anywhere in that dimension."