Bill Shorten has tried to flip the script on the cost of his climate change policies, describing them as investments instead.
Mr Shorten has also committed a future Labor government to legislating the National Energy Guarantee, even if it opposed by the coalition.
His pledge has dragged Malcolm Turnbull back into the political fray for the first time this election campaign.
As the campaign rolls its second week, the opposition leader continues to face questions about the price tag attached to his carbon targets.
The coalition claims Labor's plan to reduce emissions will cost the economy at least $35 billion and rely on buying carbon credits from overseas.
Mr Shorten flatly dismisses this estimate, but has steadfastly refused to name a price of his own.
He insists the emission reductions won't cost taxpayers a cent, and argues the cost to businesses will be comparable to the coalition's policy settings.
Facing a fresh round of interrogation in St Kilda on Saturday, the Labor leader tried to pivot to the big picture, questioning what value people placed on saving the planet.
"The problem this government has is what they call cost, I call investing," he told reporters at Luna Park.
Mr Shorten accused the coalition and some in the media of harbouring an unhealthy obsession with his policies.
Prime Minister Scott Morrison clearly enjoyed his opponent's amusement park tangle.
"He's stuck on a costings merry-go-round which he doesn't seem to be able to get off," Mr Morrison told reporters in Sydney.
Repeatedly pressed to place a price of his policies, Mr Shorten said there was no "mythical figure".
"We believe if you invest in making climate change changes now and lowering carbon pollution this will benefit the economy," he said.
The prime minister is now trying to turn the ambiguity around Labor's climate policies into an electoral asset.
"I understand Bill Shorten's policy better than he does - it's not even my policy - I don't support it," Mr Morrison said.
"I don't support it because I understand it. If you don't understand it, I wouldn't suggest you vote for it either."
The Labor leader has committed to pursuing the National Energy Guarantee - with a higher emissions reduction target - even if the framework does not receive bipartisan support.
"We will use some of the Turnbull, Morrison, Frydenberg architecture and we will work with that structure," he told reporters.
Malcolm Turnbull, who dropped the policy in the dying days of his leadership, said abandoning it altogether would lead to higher emissions and electricity prices.
He pointed out Mr Morrison was "especially" fond of the policy, which had the support of the business community and energy sector.
"However a right wing minority in the party room refused to accept the majority position and threatened to cross the floor and defeat their own government," Mr Turnbull tweeted.
"That is the only reason it has been abandoned by the government. The consequence is no integration of energy and climate policy, uncertainty continues to discourage investment with the consequence, as I have often warned, of both higher emissions and higher electricity prices."