Sousa has fired off a letter to his federal counterpart Jim Flaherty over what the provincial government says is a $641-million cut in so-called transfer payments for the current budget year.
He says Ontario is the only province to face such a drop, and he contends it also won't get special transition funding to bridge the shortfall.
Sousa writes that the transition funding — which Ottawa says was a temporary measure ending this year — should be included in the federal budget, which is to be handed down Tuesday.
Premier Kathleen Wynne has accused the Tories of balancing their books on the backs of Ontarians by cutting the amount of federal dollars returned to the province.
The decline comes from a drop in payments to Ontario under equalization, a program aimed at allowing less prosperous provinces to provide residents with a similar level of services as richer provinces.
Federal officials have said the amounts are adjusted year-to-year based on a province's economic strength, and that Ontario's share has changed because its economy improved relative to other "have-not" provinces.
But Sousa's letter says the province needs a "reliable and consistent" source of funding to help it grow the economy through projects such as the Ring of Fire.
"Ontario has always been, and continues to be, a net contributor to the federation. At a minimum, Ontario hopes to see the transition funding in your next budget to ensure fairness for Ontario families," states Sousa's letter sent on Sunday.
In a statement, Flaherty fired back by charging the Ontario government is trying "to blame the federal government for their own fiscal troubles."
Flaherty said the shift in transfer payments is "exactly how equalization is supposed to work and the Wynne governments knows that."