The Queensland government says a $5.4 billion federal investment in the Hells Gate Dam is welcome, but the project will only be approved if it makes water more affordable to northern irrigators.
It comes as Kennedy MP Bob Katter claims he received assurances from the federal government that the dam would be built to a height higher than what is being proposed.
Prime Minister Scott Morrison says funding for the dam in the state's north will be in next week's 2022/23 budget and subject to completion of the business case, expected in June this year.
Up to 60,000 hectares of irrigation would be opened up through a 2100 gigalitre dam bolstered by three downstream irrigation weirs.
"All the state government has to do is get out the big stamp and go: 'approved'," Mr Morrison told reporters on Tuesday.
State Water Minister Glenn Butcher said funding for irrigation was always welcome, but added it was interesting to see a commitment before proponents Townsville Enterprise had even completed a business case.
"Investment decisions should be informed by completed detailed business cases, the Hells Gates business case is not yet complete - this means it hasn't even received necessary federal approvals," Mr Butcher told AAP
The prime minister was very confident the business case would "stack up" and insisted the Hell Gate project hadn't been "plucked out of the air" for funding.
Queensland Treasurer Cameron Dick said the main consideration was whether the dam would actually make water more affordable for irrigators.
He said if the federal government believes that it will "absolutely lock in" the $5.4 billion pledge in next week's budget.
"We will put it through the approval process if it stacks up, but we've got to see the truth of the project from Scott Morrison, and Queenslanders have a right to be sceptical about his announcements because we've been burned before," Mr Dick told reporters.
Meanwhile Mr Katter is furious that the proposed dam would be built to 320 metres, not the 395m height he says Mr McCormack promised him in a 2021 letter.
He says that height is too low to facilitate a future Bradfield inland irrigation scheme, that he's been pushing for 40 years.
That project was dreamt up in the 1930s by engineer Dr John Bradfield, the man behind the Sydney Harbour Bridge.
The concept involves forging a new river to divert northern floodwaters to the drought-prone southwest, and a tunnel and aqueduct through the Flinders Range.
"There's just there's no way that I can defend the government and I've given the government loyalty," Mr Katter told reporters.
"I've given Scott Morrison my support and in return for that, I've been told a flagrant lie. Now whether it's intentional or not, I don't care. But I don't like being lied to.
"It's a very delicately balanced parliament, sticking a knife in my back is not very smart. If I have a reputation for brutality I've earned it."
The Queensland government is currently considering a report on a new Bradfield scheme after a review led by Ross Garnaut.
"This is an incredibly detailed and comprehensive piece of work, that requires thorough consideration," Mr Butcher said.
"The government will release the panel's report once the panel's recommendations have been fully considered."
