Queenslanders are set to fork out an extra $400 million a year ahead of a costly Olympics after a rare credit rating downgrade, an economist has warned.
The Queensland government has been called on by the opposition to reveal the true cost of its planned 2032 infrastructure after the state was dealt its first downgrade in 17 years.
The state's mammoth Brisbane Games build was cited by agency S&P Global after downgrading Queensland's credit rating from AA+ to AA, increasing the government's growing borrowing costs.
Queensland's Liberal National government blocked an opposition motion in parliament on Tuesday that would have forced it to reveal Olympic venue costs.
However, University of Queensland economics professor John Quiggin warned there would likely be Olympic infrastructure blowouts amid the state's rising debt.
S&P Global projected the state's debt to rise to about $216 billion by 2029-30, fuelled by the massive 2032 Brisbane spend.
Prof Quiggin estimated that would add an extra 0.2 percentage points to Queensland's borrowing costs.
"As they turn over their debt, we'll actually be paying that much extra in interest, offset by whatever happens to the general rate of interest set by the Reserve Bank," he told AAP.
"We've got about $200 billion of debt, and when that's all rolled over, getting past the Olympics, we'd be paying an extra of about $400 million a year.
"That's assuming nothing else changes, which of course it will."
But Prof Quiggin said the state was better off going ahead and building the necessary infrastructure.
"We're still not in the kind of territory where we really need to worry," he said.
"You can argue about staging the Olympics in the first place, but we're stuck with it."
The Labor opposition claimed the downgrade was fuelled by uncertainty around Olympic infrastructure, moving the motion in parliament to force the government to reveal 2032 costs that was voted down.
"Queenslanders deserve to know how much the Olympic and Paralympic Games are really going to cost because they are the ones who will pay if the projects blow out," Opposition Leader Steven Miles said in a statement.
"David Crisafulli and his treasurer's poor fiscal management has already resulted in a credit rating downgrade and an Olympic-size blowout could result in another."
However Mr Janetzki reiterated claims the government had inherited the downgrade from the former Labor administration which he accused of "fiscal vandalism".
He also pointed the finger at the federal government, saying the downgrade was "set in stone" by Treasurer Jim Chalmers for changes to negative gearing that he said had hit Queensland stamp duties.
Lobby Group GamesWatchDog2032 said the credit downgrade was "a warning shot we can't ignore".
It warned of the long-term financial impact, saying the danger was not simply the Games construction bill.
"It is the potential long-term burden of debt, interest, maintenance and operating costs associated with infrastructure that may have limited use after the Olympic caravan leaves Brisbane in 2032," it said in a statement.
