TORONTO - Prime Minister Stephen Harper's Conservative government risks losing vital votes in Ontario if it doesn't start treating Canada's largest province with more financial fairness in the next federal budget, Premier Dalton McGuinty warned Monday.

Ontario does not get funded at the same level as other provinces when it comes to federal support for health care, post-secondary education, roads and bridges and help for unemployed workers, McGuinty said, renewing a familiar refrain that political observers are sure to hear more of in the coming election year.

"Any way you look at it, Ontario is being shortchanged by billions of dollars annually," he said.

"If the prime minister is intent on demonstrating his commitment to the people of Ontario, then he's going to have to treat Ontario families fairly."

With a federal election possible in the spring, Harper will need to fix the so-called fiscal imbalance in the next budget if he wants to get support from Ontario voters, McGuinty said.

Those same voters head to the polls in October to pass judgment on the provincial Liberals, who were elected in 2003.

"On behalf of the people of Ontario, I'm asking the prime minister to keep in mind what Ontarians would be looking for in this particular budget is fairness," McGuinty said. "At present, we are not being treated fairly."

McGuinty is also angry with the Conservatives for claiming they have honoured a $6.8-billion deal he signed with the former federal Liberal government. Ontario's funding under that deal is as much as $3 billion short, he said.

The federal government has said it met the terms of the deal by setting up special trust funds for all provinces for things such as post-secondary education, housing and public transit - an argument McGuinty flatly rejected.

"What they have effectively done is say, 'Here are new monies available for all Canadians in all provinces, and by the way McGuinty, that special deal that you had with (Paul) Martin, we're now going to account for that with these monies that were distributed to all Canadians,"' he said.

"The purpose of that deal was to help bring a little bit more fairness to our relationship with the federal government."

McGuinty said he was encouraged by the recent federal Liberal leadership convention, where delegates adopted a resolution acknowledging the fiscal imbalance. Newly minted leader Stephane Dion, however, doesn't agree.

"We'll have to keep working with him, obviously," McGuinty said.

Last month, federal Finance Minister Jim Flaherty said the Tories intend to move forward in their next budget with what he called a "principled approach" to equalization and fiscal transfers.

McGuinty is opposed to any increase in the $12-billion revenue-sharing equalization program for poorer provinces until Ontario starts getting the same levels of per-capita funding as other provinces.

Other provinces are split on the funding formula for equalization and whether the newfound resource wealth of the so-called "have-not" provinces should be included in the calculation.

The premiers of the four Atlantic provinces called on Ottawa last month to immediately devise a revised equalization formula, but they were split on the approach.

Nova Scotia Premier Rodney MacDonald wants resource revenues included in calculating equalization benefits, as does New Brunswick's Shawn Graham and P.E.I. Premier Pat Binns.

But Newfoundland Premier Danny Williams is fiercely opposed to the idea, and will join Saskatchewan Premier Lorne Calvert in a cross-Canada tour seeking support for their fight with Ottawa over the equalization program.