The governing Liberals used their majority power to quash an opposition effort to hold parliamentary hearings into why Canada’s foreign ministry called two former diplomats to caution them against contradictory public messaging on China, and why they were told this was at the behest of the Prime Minister’s Office.

A senior Liberal, Rob Oliphant, Parliamentary Secretary to the Foreign Affairs minister, called the Conservative- and NDP-backed motion a political ploy that threatened to distract the government from “patiently, consistently and constantly working” to secure the release of two Canadians arrested by Beijing and damaged trade relations between Canada and China.

Conservative Leader Andrew Scheer, however, accused the Liberals Tuesday of covering up an effort to influence the public statements of former diplomats. “The fact they shut down this investigation shows there is something to hide. If there was nothing to see, Justin Trudeau should have welcomed this committee and allowed committee members to get the bottom of it.”

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At the heart of the matter is a clash of opinion on whether Canadians should travel to China in the wake of the arrests of former diplomat Michael Kovrig and entrepreneur Michael Spavor. The two men were taken into custody by Beijing – and accused of espionage in the days after Canada detained a senior Chinese tech executive on an extradition request from the United States.

The Canadian government disagrees with former ambassador David Mulroney, who has publicly advised Canadians to avoid all non-essential travel to China.

On Monday, Mr. Oliphant said the government believes it’s still safe for Canadians to travel to China today.

“We are saying it is still safe,” Mr. Oliphant said in an interview. “These, I think, were very targeted abductions,” he said of the arrests of Mr. Kovrig and Mr. Spavor.

“We don’t have any sense that Canadians going to China would be in any different situation than they have been in previous years.”

Monday’s effort to launch a Parliamentary hearing followed reporting by The Globe and Mail.

Mr. Mulroney, a career foreign-service officer, said Global Affairs Canada – citing a request from the PMO – asked him to check with the department before he makes future public statements on Ottawa’s China policy, citing the “election environment.” Mr. Mulroney served as envoy to Beijing between 2009 and 2012.

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"In this time, he said, of high tension and in an election environment, we all need to be very, very careful," Mr. Mulroney recounted. "He said ... 'I've been asked by PMO: Before you comment on aspects of China policy, it would be good if you called in and got the latest from us on what we're doing.'"

The official in question was Paul Thoppil, the Department of Global Affairs' assistant deputy minister for Asia Pacific.

Guy Saint-Jacques, another former envoy to Beijing, said he, too, received a call from Mr. Thoppil. Mr. Saint-Jacques, who was Canada’s envoy to China between 2012-16, told The Globe and Mail he found the directive to be particularly odd given that it concerned an authoritarian state. “Especially having served in China and knowing how they try to control messaging there,” he said.

Mr. Saint-Jacques characterized the way the message was delivered as "a bit clumsy," adding Mr. Thoppil "wanted me to know that PMO just wanted him to relay the hope that we could all speak with one voice to support the strategy of the government."

Mr. Saint-Jacques said the tone of his conversation with Mr. Thoppil appears to have been different from what Mr. Mulroney experienced. He said he can see how Mr. Mulroney might have felt the government was asking him to clear public comments first. "In my case, I did not feel that. But I can understand that one could come to that conclusion when they say we should speak with one voice."

The government has never suggested Mr. Mulroney mischaracterized the contents of his conversation with Mr. Thoppil.

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But the Prime Minister’s Office last week said it would never try to prevent a former diplomat from speaking freely. Foreign Affairs Minister Chrystia Freeland’s office echoed this. “As for the two former ambassadors, Minister Freeland has immense respect for both and has never and would never seek to interfere with their free and independent contribution to the public debate,” spokesman Adam Austen said.

Asked why Mr. Thoppil repeatedly invoked the PMO in the calls to the former envoys, Mr. Oliphant suggested it might have been an effort to get their attention.

“I have no idea. I know that even as a backbench MP when someone wants to have influence they will often invoke the name. That could be it,” Mr. Oliphant said.

“A new [assistant deputy minister] had a job he thought he wanted to get done by talking to two former diplomats.”