The comments come after Adani last month threatened to walk away from the project if it wasn't given a "royalties holiday" by the Queensland Labor government.

Suggestions of a royalties holiday sparked infighting between Labor's left and right factions, delaying Adani's announcement until a deal on the concession was finally struck in late May.

Within a week, Adani had announced it planned to proceed with the mine, but less than 24 hours later, Adani's own comments have again placed the project in doubt.

GetUp! campaign director Sam Regester said Adani was holding Australian taxpayers to ransom.

"After threatening to walk away until it bullied a juicy royalty deal out of the Queensland Government, Adani has lasted less than a day before again threatening to take its bucket and spade and go home," he said in a statement.

“It must be be quite humiliating for [Queensland] Premier Palaszczuk to bend over backwards and give Adani a huge royalty deal and free water only for them to again threaten to walk away unless they get a billion dollars as well.”

When contacted by BuzzFeed News, an Adani spokesperson denied the comments amounted to a threat to walk away from the project, saying the NAIF funding remains critical.