Bill Shorten has adjusted Labor’s position on the Adani Carmichael coalmine again by dropping threats to use an investigation into alleged doctoring of scientific reports to cancel its licence.

Shorten has been accused of inconsistency after offering highly qualified support for the mine last year, threatening to revoke its licence in January and February, stating that he does “not support” the mine on Monday and reversing the licence threat on Tuesday.

In January Shorten used a speech at the National Press Club to suggest a Labor government may do more to stop the Adani mine.

Guardian Australia reported that Adani submitted an altered laboratory report while appealing a fine for contamination of sensitive wetlands on the Queensland coast near the Great Barrier Reef.

While launching Ged Kearney’s campaign for Batman, Shorten said the “scandalous allegation” – if true – would mean that Adani did deserve a licence to operate a coalmine.

Last week shadow cabinet discussed the mine and the balance of views was to oppose cancelling Adani’s licence, after which Shorten stressed that to do so would be a “sovereign risk” that Labor could not support.

But on Monday Shorten said he did not support the mine, which prompted a backlash from one unnamed frontbench colleague who reportedly told Sky News that Shorten was “kidding himself” if he thought Labor could outflank the Greens on Adani to win the Batman by-election.

At a press conference in Adelaide on Tuesday Shorten was asked repeatedly about Adani and defaulted to a position that he was “increasingly sceptical of the Adani proposal” and “not a fan” because it did not stack up environmentally and commercially.

Shorten said it would be a sovereign risk to “tear up contracts” and the same applied to revoking the licence.

Former Australian Conservation Foundation president, Geoff Cousins, revealed last week that Shorten had told him he was prepared to back a proposal to revoke the licence using a provision of the Environment Protection and Biodiversity Conservation Act and new information coming to light about the mine.

Asked if he could still use the “new information” clause to change Labor’s position again in government, Shorten dismissed the question as a hypothetical.

Shorten again called on the Turnbull government to investigate whether Adani tampered or falsified reports. “Then there was the debate that’s been raised in the Guardian which says these reports were falsified … Let’s not confuse that with the whole issue of sovereign risk,” he said.

“I don’t support it because it doesn’t add up commercially and environmentally. It is the same project and proposition.”

Federal Labor’s position is now at odds with Queensland Labor. On Tuesday the premier, Annastacia Palaszczuk, told parliament “the government supports Adani as long as it financially stacks up … We have been clear about that from day one”.

The federal energy and environment minister, Josh Frydenberg, said Shorten was “the chameleon of Australian politics” and could not be trusted to maintain a consistent position on the Carmichael mine.

On Tuesday Fairfax Media reported the Export Finance and Insurance Corporation had plans to indirectly support the Carmichael mine by financing a business that would supply the project.

It said the body, which provides loans to exporters was also considering inquiries from other Adani suppliers and held discussions with Adani representatives as recently as last month.

The principal of Environmental Justice Australia, David Barnden, told Guardian Australia that Efic had a “broad mandate” to assist exports and the fact it supported a business in Adani’s supply chain suggested it “is familiar with the project and could provide more support to make the project proceed”.

Barnden said the trade minister, Steve Ciobo, could not direct Efic to give loans unless it was in the national interest and it would be “extremely bold” to attempt to finance the coalmine indirectly in this way given the impact of climate change.

At a doorstop in Canberra, Frydenberg said it was a commercial decision for Adani whether to proceed since a proposed Northern Australia Infrastructure Facility loan for the rail line was not proceeding.

“I’m not aware of any other of any other commonwealth money at this stage that is going to the project,” he said. “There is no case before me about any money from the commonwealth.”