Liberal members of the House committee on foreign affairs Tuesday shut down opposition parties' attempt to launch an investigation into claims a federal official pressured two former diplomats over their statements on Canada-China relations.

Opposition parties allege the government tried to muzzle two ex-ambassadors who have been outspoken about Canada's ongoing diplomatic conflict with China. The bid to open an investigation failed after the Liberals, who hold a majority of the committee's seats, defeated the motion in a 5-4 vote Tuesday afternoon.

The Globe and Mail reported last week that former Canadian ambassador to China David Mulroney said Paul Thoppil, an official with Global Affairs Canada, instructed him to clear any public comments on Canada's China policy with the department beforehand. The official reportedly cited the "election environment" and said he was passing on a request from the Prime Minister's Office.

Mulroney told the Globe and Mail Thoppil also cautioned against telling Canadians to suspend non-essential travel to China. The former diplomat said he found the request troubling and claimed the department official implied he should soften his tone.

Another former ambassador, Guy Saint-Jacques, also said he had been contacted by Thoppil. But in several recent interviews he said he didn't interpret the government's outreach as an attempt to filter his views.

David Mulroney, Canada's former ambassador to China, shown in 2009, told the Globe and Mail he had been instructed by an official with Global Affairs Canada to clear any public comments on Canada's China policy with the department beforehand. (Pawel Dwulit/Canadian Press)

Last week, Conservative and NDP MPs wrote a letter to the committee asking for a summer meeting to talk about the allegation.

"We believe it is incumbent on the committee to study these matters and ensure that Canada's non-partisan public service is not being unduly exploited for political purposes," they wrote.

PM says his office didn't pressure ex-diplomat

Ahead of the committee meeting, Prime Minister Justin Trudeau told reporters in Vancouver on Monday that his office did not pressure Mulroney to avoid recommending that Canadians avoid non-essential travel to China.

Conservative Party Leader Andrew Scheer said Trudeau's comments mirrored ones the prime minister made after the SNC-Lavalin scandal erupted, when the PMO was accused of exerting inappropriate influence over the office of then-attorney general Jody Wilson-Raybould.

"Justin Trudeau's office stands accused once again of political interference," Scheer said. "Today he borrowed from the SNC playbook."

Conservative committee member MP Leona Alleslev said she was "not surprised, but disappointed" when the Liberals voted against an investigation. Alleslev said the opposition hoped to call several witnesses: Foreign Affairs Minister Chrystia Freeland, Thoppil, Mulroney and St-Jacques.

In an interview with CBC's Power and Politics Tuesday, Saint-Jacques said he would have testified before the Foreign Affairs Committee, if called. But he said he didn't know what help his evidence would provide.

"I never felt that they were trying to muzzle me or that they were threatening me," Saint-Jacques said. "I think basically it is another example of miscommunication."

Saint-Jacques also told Power and Politics host Vassy Kapelos that Foreign Affairs Minister Chrystia Freeland called him last week to assure him personally that the government wasn't trying to silence him.

Opposition playing politics?

Parliamentary secretary to the minister of foreign affairs Rob Oliphant accused the Conservatives of calling an emergency committee meeting purely to score political points. Oliphant said politicians on all sides should not be playing politics with the lives of the two detained Canadians — entrepreneur Michael Spavor and former diplomat Michael Kovrig — caught up in the diplomatic and trade confrontation between Canada and China.

"There are times in politics, there are times in public policy, there are times in Canadian shared life that we let some of that go," Oliphant told the committee. "There should be nothing more on our minds than assuring their safety and considering their well being."

In addition to the lives of the two "arbitrarily detained" Canadians, Oliphant called on the members to remember the plight of canola farmers and meat producers whose livelihoods also have been affected by the diplomatic row.

Oliphant also echoed a statement from Global Affairs Canada, which said the department's message to the former diplomats "was not clearly communicated."

Message wasn't clear: GAC

"We undertake such engagement in part to ensure informed public discussion of important foreign policy issues so that comments of others such as former diplomats are well informed by current circumstances. The call with Mr. Mulroney was made with this intention," wrote Sylvain Leclerc in an email.

"We welcome the views and advice of informed Canadians such as Mr. Mulroney on these complex issues and regret that this message was not clearly communicated. There was no intention, nor was there any instruction from anyone, including the PMO, that Mr. Mulroney clear his public comments with the government."

The Liberal government tried to distance itself earlier this summer after former cabinet minister John McCallum, who was fired as ambassador to China in January amid mounting tensions between Canada and China, said he had warned former contacts in China's Foreign Affairs Ministry that any further "punishments" imposed on Canada's exports could trigger a change of government that would be unfavourable to Beijing.

Prime Minister Justin Trudeau speaks at the Canadian Coast Guard Kitsilano Base in Vancouver on Monday. He said his office did not pressure a former Canadian ambassador to avoid recommending that Canadians cease non-essential travel to China. (Darryl Dyck/THE CANADIAN PRESS)

"Anything that is more negative against Canada will help the Conservatives, [who] are much less friendly to China than the Liberals," McCallum was reported as telling the South China Morning Post.

The Conservatives have asked the Canadian Security Intelligence Service to investigate McCallum's statement.

Diplomatic and trade relations with China have been deteriorating since Canada began extradition proceedings against Meng Wanzhou, a top executive with the Chinese telecommunications firm Huawei. Wanzhou faces charges in the United States of fraud and violating international sanctions against Iran.