Open this photo in gallery Conservative Party of Canada's foreign affairs critic Erin O’Toole is pictured in Ottawa, Ont. Sean Kilpatrick/THE CANADIAN PRESS

The Conservative Party wants Prime Minister Justin Trudeau to immediately telephone China’s President to seek the release of two imprisoned Canadians, and to inform the people of Canada whether it is safe to travel to China.

The party’s foreign affairs critic, Erin O’Toole, said it is baffling that Mr. Trudeau called U.S. President Donald Trump on Monday to discuss the jailed Canadians, but has been reluctant to speak directly to Chinese President Xi Jinping.

"The Prime Minister’s refusal to call the Chinese President to begin to de-escalate the situation has many Canadian families deeply concerned,” Mr. O’Toole said at a news conference on Tuesday. “They are questioning travel to China and are concerned about the well-being of their family members working there.”

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Mr. O’Toole said it is important for Mr. Trudeau to call China’s leader to demonstrate that he is “seized with the situation and has a personal interest in its resolution.”

The Conservatives also want Ottawa to clearly state whether it is safe to visit China since former Canadian diplomat Michael Kovrig and entrepreneur Michael Spavor were detained last month in what appears to be reprisal for Canada’s arrest of Huawei Technologies Co. Ltd. executive Meng Wanzhou.

Canada has not issued a travel update for China, even though the United States renewed its advisory last week, cautioning U.S. citizens they could face arbitrary arrest amid heightened diplomatic tensions over the U.S. request that Canada extradite Ms. Meng on allegations of possible fraud relating to U.S. sanctions against Iran.

On Monday, former Liberal foreign affairs minister John Manley, who recently retired as chief executive of the Business Council of Canada, said he would not travel to China and is advising businesses associates to do the same.

“The government needs to either update the travel advisory for China or provide Canadians with the assurances that there are no risks as a result of the current diplomatic dispute,” Mr. O’Toole said.

The Prime Minister’s Office did not respond to requests for comment on the demands, but the office of Foreign Affairs Minister Chrystia Freeland accused the Official Opposition of playing partisan politics.

“In recent weeks, the Prime Minister, the foreign minister and Canada’s ambassador to China have been closely engaged on this important matter," said Ms. Freeland’s communications director, Alex Lawrence. “Canadian officials have met both Mr. Kovrig and Mr. Spavor, and we continue to seek regular consular access. Turning this into a partisan issue is entirely irresponsible. Every action our government takes is focused on the safety and security of these two Canadians. "

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David Mulroney, a former Canadian ambassador to China, cautioned against calls for Mr. Trudeau to personally urge Chinese leaders to release Mr. Kovrig and Mr. Spavor.

“In the Chinese system, if you get a ‘no’ from the very top, that no is pretty final. So I’d work through the system carefully and do everything short of asking that ultimate question so we can keep these issues alive and on the table,” he said.

He said Mr. Trudeau will likely find opportunities on the margins of international meetings to raise the issue with Chinese leaders.

Mr. Trudeau has been marshalling international support to press Beijing to free the two Canadians. In addition to Mr. Trump, he spoke on Monday to Japanese Prime Minister Shinzo Abe.

Mr. Trump said he was firmly committed to pushing China to free the Canadians and Mr. Abe "reiterated the importance of respecting and adhering to justice and the rule of law,” Mr. Trudeau’s office said.

Britain, Germany, France, the European Union and Australia have also called for the release of the Canadians.

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Mr. Mulroney called the U.S. travel advisory for China the “top of the line.”

But he said he thinks Canada’s current advisory is good. It warns Canadians to “exercise a high degree of caution” because of “isolated acts of violence, including bombings and protests.” It also cautions that Chinese authorities may detain foreigners for up to six months without formally arresting them for behaviour and activities Beijing considers a danger to national security.

Mr. Mulroney said Canadian tourists to China are not at risk, but “people whose business it is to go off the beaten track and meet Chinese people and explore difficult and sensitive topics” could be. He said that would include former diplomats, people who work for non-governmental organizations and journalists.

Consular officials visited Mr. Spavor on Tuesday for the second time since his Dec. 10 arrest, but provided no further details on his treatment.

Global Affairs said embassy officials in Beijing are seeking “further access” to Mr. Kovrig. Canada’s ambassador to China, John McCallum, visited Mr. Kovrig on Dec. 14, shortly after his arrest.