The government eliminated the mandatory long questionnaire in late June, arguing it was intrusive and the threat of jail was overly coercive. (CBC)

Ontario and Quebec have launched a formal complaint against the federal government's decision to axe the mandatory long-form census, calling the move a "mistake" that will have serious consequences.

Cabinet ministers from both provinces have written to federal Industry Minister Tony Clement, requesting he reinstate the long-form census survey "as soon as possible."

The two-page letter dated Sept. 27 and obtained by The Canadian Press argues forcefully that the census decision will hamper provincial support for education, innovation and economic development.

The lack of data from the census long form will also further impair labour mobility and governments' understanding of the country's labour market, the ministers said.

The letter is signed by Ontario Minister of Training John Milloy, Quebec Education Minister Line Beauchamp and Quebec Employment Minister Julie Boulet.

Some provinces spoke out against the federal government's census move during the summer, but the formal complaint from Ontario and Quebec escalates the opposition.

"We believe that the decision by the federal government to eliminate the census long form was a mistake and that it will impact negatively on the provision of services to the people of our provinces," it says.

"We therefore urge you to reverse this course of action as soon as possible."

Government not budging

The federal Conservatives have been on the hot seat all week over their move last June to eliminate the mandatory long census and replace it with a voluntary survey.

The three opposition parties backed a motion Tuesday to revive the mandatory long-form census. The Liberal motion, scheduled for a vote Wednesday afternoon, demands the return of the mandatory long questionnaire, minus the threat of jail time.

But Clement has said plainly that his government will not respond to the motion if it passes the Commons.

Clement reiterated on Wednesday that the decision to replace the census with a voluntary survey, mailed to more households, was a way to strike a balance between the privacy rights of Canadians and the need for the information by government policymakers and outside groups.

He also downplayed the importance of Ontario and Quebec's formal complaint.

"It's the same tune that they've had from the beginning," the minister told reporters outside his party's caucus meeting on Parliament Hill. "I respect their position, but we believe that our's is the fair and reasonable position."

Changes challenged in court

The census issue was also being debated a few streets over on Tuesday inside a Federal Court hearing, where the Federation of Francophone and Acadian Communities is arguing the elimination of the long census will violate provisions of the Official Languages Act. It is asking the court to bring back the mandatory long-form questionnaire as soon as possible.

The federal government made its case to Justice Richard Boivin on Tuesday that nothing in the act directs the government to use census data as it works to nurture official language minority communities in Canada. It also argued that there is no evidence the new voluntary survey won't provide usable data.

The court has heard that Statistics Canada cannot make changes to the 2011 census process past the middle of next week, because of a complicated administrative schedule.

Liberal MP Carolyn Bennett also has a private member's bill to bring back the mandatory long form that is expected to hit the Commons by mid-October. She argues the government would have a hard time blocking the bill because it would actually save money to reinstate the long form.