Canada's rebuke of China after the jailing of a prominent legal activist represents the country's strongest, most public criticism of Chinese human rights in recent years, experts say.

"Canada deplores the sentencing of Xu Zhiyong," a statement from Canada's ambassador to China, Guy Saint-Jacques, read, after Mr. Xu was sentenced over the weekend to four years in prison for "gathering a crowd to disturb public order."

As founder of civil rights group New Citizens Movement, Mr. Xu has called on Chinese officials to disclose their personal wealth and fought for the right of rural children to attend city schools.

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Mr. Saint-Jacques went a step further too, calling on the Chinese government to "end the harassment and unjust detention" of other Chinese dissidents, including Nobel Peace Prize winner Liu Xiaobo and his wife Liu Xia.

"Chinese citizens like these who peacefully work to improve their country should be free from intimidation, harassment and prosecution," Mr. Saint-Jacques wrote.

His statement comes amid criticism that Ottawa is shifting the country's foreign policy focus to "economic diplomacy" – and, some say, away from human rights.

Charles Burton, a political science professor at Brock University who specializes in Canada-China relations, said that Mr. Saint-Jacques's unusual statement is a direct response to such criticism.

"I think that they're sending out a very strong signal through Mr. Saint-Jacques that this is not the case, and that Canada continues to put human rights at the centre of Canada-China relations," he said.

In the past, Canada has favoured a more "quiet diplomacy approach," said Mr. Burton.

During his trip to China in 2012, Prime Minister Stephen Harper avoided all mention of Mr. Liu – the 2010 Nobel Peace Prize winner unable to attend his own prize ceremony because he is serving an 11-year sentence for "inciting subversion of state power."

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His wife, Liu Xia, has been under 24-hour watch by Chinese guards since, prevented from leaving her apartment or communicating with the outside world.

Mr. Burton added that the statement coming directly from the ambassador – who the Chinese deal with on a day-to-day basis, as opposed to the foreign minister – indicated that the government "plans to raise the volume" on human rights.

But while he agreed that Mr. Saint-Jacques's statement is unusual, Errol Mendes, a law professor and former director of the Human Rights Research and Education Centre at the University of Ottawa, said he's not optimistic the words will be reflected in policy.

"Our approach to foreign policy has become so tattered and so ad hoc, that I have a feeling this is just more inconsistency," he said.

"When he first got elected, he kept on making very general statements about human rights in China," Mr. Mendes said of Mr. Harper.

And then, "he went silent," Mr. Mendes said.

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"It just shows you that we're a little bit like the Keystone Kops for China."