Deb Frecklington says the Liberal National Party would spend less than the state government but can't say how she'd pay down soaring debt if elected Queensland's premier.
The state's Labor government has been slammed by opposition MPs for steering the state towards a $90 billion debt in four years.
But the opposition leader hasn't said how she would pay it back.
"Who knows what the state of the finances would be after the 2020 election," Ms Frecklington said on Thursday.
"We need to ensure that we get an opportunity to look at the state of the finances before I can make any wild predictions there. But what I would say, is that we will control government expenses."
Ms Frecklington promised a ten-year freeze on all mining royalties and a new scheme to pay for hospitals and schools in her response to Treasurer Jackie Trad's second budget.
She also pledged $8 million for mineral exploration in the state's north west, ruled out new taxes, asset sales and forced redundancies in the public sector.
Ms Trad, who tabled her budget on Tuesday, said the government's record spending across multiple sectors is attainable and will stimulate more jobs across the state.
Australian Associated Press