Speaking to a business crowd at the Toronto Board of Trade, Duncan said the province cannot waver on the strong actions needed to drive down the current $14.4-billion deficit by 2017-18 or even earlier.
"There will be difficult choices," Duncan said. "All the choices haven't been made."
And Ontario's debt load can not be lowered just by "cutting waste" — as the opposition parties have suggested, he said.
Instead, the province needs to keep its average annual growth rate at 1.5 per cent, and that can only be achieved by unpopular decisions like decreasing program spending and freezing public-sector wages.
That means that public employees need to understand that fundamentally, the government needs to choose between wage freezes or job losses, Duncan said.
"It's not calculus. It's not linear algebra. It's arithmetic."
Several times during his 35-minute speech, the minister took political jabs at the alternative economic plans offered by the opposition.
Duncan said the Progressive Conservative Leader Tim Hudak's promised tax cuts would leave a more lasting impact on the province than those during the era of his predecessor, Mike Harris.
"Don't be seduced..." he said. "That plan will land this problem into a fiscal abyss that will make what's going on in the United States look easy by comparison."
The minister said the Tory plan to lower taxes would amount to billions of dollars in cuts to health, education and social services.
And if the Liberals were to go with the NDP's plan of "inaction," by not freezing public sector wages and instead, raising the province's harmonized sales tax — Duncan said the province would be en route to double its deficit to $30 billion by 2017-18.
"These numbers are not going to go away," he said.
"They will disappear over time if we stick to a strong balanced plan. So regardless of who, and which party forms the next government, these are challenges we are all facing."
Progressive Conservative MPP Lisa MacLeod said Duncan's remarks were "out of touch" and came from someone who already has one foot out of the door. The minister announced in October that he will not be running for public office in the next election.
"It was very hard to take him seriously today. It was pretty much a swan song for him and a retirement party," she said. "He really isn't someone who will be involved in the decision making in the province's finances in the next five years.
New Democrat finance critic Michael Prue defended his party's economic plan, saying in a statement that during the 2012 budget discussions, they "were able to deliver increased support for affordable childcare, hospitals and our most vulnerable neighbours, and all without adding a nickel to the deficit."