The prime minister has seized on claims a Labor government could kill off the Adani coal mine in Queensland, accusing Bill Shorten of playing up to a "big greenie" over workers.
"Doesn't that show what a duplicitous person we have in Bill Shorten," Malcolm Turnbull told reporters in Canberra on Wednesday.
The coalition attack comes after former Australian Conservation Foundation president Geoff Cousins recounted a private conversation in which Mr Shorten raised the prospect of cancelling the mine's licence.
The $16 billion Carmichael mine in the Galilee Basin is expected to create thousands of jobs for Townsville and Rockhampton residents.
"This is a guy who goes out to work sites, he goes out to see the CFMEU miners at Oakey and he tells them he's backing them, he's right behind them," Mr Turnbull said.
"And then he goes to see Geoff Cousins, who is a big greenie, a big environmentalist, and he says to Cousins privately, when no coalminers are listening, when no voters in North Queensland are listening, he says 'Don't you worry, Geoff, when I'm prime minister, I'll cancel its licence'."
Businessman Mr Cousins said he and Mr Shorten spoke last month when the opposition leader made an unofficial visit to north Queensland.
He cited Mr Shorten as telling him: "When we are in government if the evidence is as compelling as we presently believe it to be regarding the approval of the Adani mine, we will revoke the licence, as allowed in the act. That's a clear policy."
Mr Shorten spent two days with Mr Cousins discussing the mine's impact on the Great Barrier Reef and climate change.
"He said the reason he wanted to get that first-hand knowledge was because he was planning a firmer policy position on Adani," Mr Cousin's told ABC television's 7.30 program.
Mr Shorten's office confirmed he sought a meeting with the Australian Conservation Foundation and Mr Cousins to discuss the mine.
"The visit renewed Bill's convictions on the importance of protecting the reef and the environment," the spokesman said.
"It's no secret that Bill is deeply sceptical of the proposed Adani coal mine. He believes if it cannot stack up environmentally or commercially, it should not go ahead."
Earlier this month, Mr Shorten questioned whether north Queenslanders were being "led on with the promise of fake jobs and they're never going to materialise".
He was speaking at the launch of Labor's campaign to retain the marginal federal seat of Batman in Melbourne against a strong challenge from the Australian Greens, who openly oppose the mine.
Australian Associated Press