Federal Finance Minister Jim Flaherty said his call to Ontario to reduce corporate taxes is not a personal attack on Premier Dalton McGuinty but a "wake-up call" to increase productivity and competitiveness.

Flaherty made the comment in a letter sent to McGuinty Monday, insisting the premier must "focus on getting the economic fundamentals right" in order for Ontario to "regain its rightful place as a leader in our economic union."

It was the latest in a series of controversial exchanges between the two politicians stemming from last week's federal budget. The finance minister faced criticism Monday for his earlier comment that Ontario is the "last place" in Canada to start a business because of its high corporate taxes.

Liberal MP John McCallum lambasted Flaherty during question period for taking the "unprecedented step of trashing the investment climate of his own province, telling the world to avoid investing in Ontario."

Flaherty, a former Conservative MPP, defended his statements as facts, saying the highest taxes on new business investment in Canada are in Ontario.

"The result is that the policies of the McGuinty government are harming manufacturing in the province of Ontario at the very time that we need to stimulate growth," Flaherty said.

For his part, McGuinty defended the province Monday, saying it needs federal help to cope with tough economic times, not "unacceptable" criticism from Flaherty, who may be discouraging business investment.

"What we need is a federal government that is prepared to champion the economy as a whole, including the Ontario economy," McGuinty told reporters at the University of Ottawa after a funding announcement.  

In December, he said the Ontario government eliminated its capital tax on resource-based industries, including manufacturers. He said Ontario has a comprehensive plan that includes not only lowering business taxes but also investing in health care, education, infrastructure and business partnerships.

McGuinty said Ontario plans to reduce business taxes by $3 billion.

The premier said Ontario needs the help of the federal government as it copes with a downturn in its manufacturing and forestry sectors. Economists have suggested that if the U.S. dips into a full-blown recession, the impact will be felt the most in Ontario and Quebec.

"What I'm saying to the federal government is we need your help. We need a real committed partner to help us transition through this challenging period of time," he said.

McGuinty wrote a letter to Prime Minister Stephen Harper on Sunday, saying Flaherty's job is to work with the provinces and territories to promote the Canadian economy, not to single one out for ongoing criticism.