OTTAWA -- Justin Trudeau made it clear Tuesday that he would not interfere with the Ontario government's use of the Constitution's notwithstanding clause to forge ahead with plans to cut the size of Toronto city council, even though he was disappointed in the decision.

Trudeau said he and his government are staunch supporters and defenders of Canada's Charter of Rights and Freedoms because it provides a set of guarantees that Canadians value and identify with as fundamental safeguards.

"So any time a government chooses to invoke the notwithstanding clause to override the charter's protections, it has to be done deliberately, carefully and with the utmost forethought and reflection," Trudeau said during an event in Winnipeg.

"But I won't be weighing in on the debate on how big Toronto municipal council should be," he added. "We shall respect and allow Ontarians to judge whether their government is doing a good thing or not."

The notwithstanding clause gives provincial legislatures or Parliament the ability to usher in legislation that effectively overrides provisions of the Charter of Rights and Freedoms, but only for a five-year period.

Ontario Premier Doug Ford took the rarely used step Monday after a judge said it was unconstitutional to slash the number of city council seats in the middle of a municipal election without consultation.

Toronto Mayor John Tory called the move a "gross overreach" of the province's powers and said in a tweet Monday night he had met with Trudeau, who was in the provincial capital for a women's summit, to discuss his concerns.

Federal Intergovernmental Affairs Minister Dominic LeBlanc said the notwithstanding clause is an extraordinary part of the Constitution that should be used only in the most exceptional of cases.

Like the prime minister, LeBlanc stopped short of signalling federal intervention, saying Ontarians "will ultimately judge the actions of their provincial government."

LeBlanc's suggestion the notwithstanding clause could be invoked in a legitimate emergency makes sense, said Michael Pal, an associate professor of law at the University of Ottawa.

Beyond such circumstances, the most important thing a government in Ottawa can do to play a leadership role in preserving rights and freedoms is to refrain from ever relying on the provision, he added.

"If the federal government ever starts using the notwithstanding clause, it's very hard to say to a province, 'Oh, you shouldn't use it either.' So the federal government really sets the tone."

Caroline Mulroney, the daughter of former prime minister Brian Mulroney, serves in Ford's cabinet as attorney general. The senior Mulroney denounced the notwithstanding clause in 1989 as a "major fatal flaw" of the Constitution.

Appearing at an event in Ottawa on Tuesday, he said that while in office he "had no interest in using it, no matter what."

"And, no, I haven't discussed this with my daughter."

A spokesman for Conservative Leader Andrew Scheer had no immediate comment on Ford's move.