As Prime Minister Justin Trudeau selected another political appointee for one of Canada’s most high-profile diplomatic posts, a former senior ambassador says the prime minister fails to understand the importance of career diplomats.

Bob Rae’s appointment as the next Canadian ambassador to the UN is the latest in a series of political appointees taking the most prolific diplomatic posts in the Canadian foreign service. That list includes the appointment of Mr. Rae’s predecessor Marc-André Blanchard, Dominic Barton and former immigration minister John McCallum as ambassadors to China, former privy council clerk Janice Charette as high commissioner to the United Kingdom, Isabelle Hudon as ambassador to France, former foreign affairs minister Stéphane Dion as ambassador to Germany and envoy to the EU, and David MacNaughton as former ambassador to the U.S.

Former ambassador to China Guy Saint-Jacques, who, during his time in the foreign service, was responsible for leading the heads of mission nomination process, said the successive selections of political appointees shows that Mr. Trudeau (Papineau, Que.) doesn’t understand foreign affairs and he doesn’t understand the importance of diplomacy.

“Diplomacy is not show business,” he said, adding that Mr. Trudeau has had an approach to appoint people who are well known. “He neglects the fact that you need experience and competent people.”

Mr. Saint-Jacques said the selection of political appointees sends a “bad message” to career diplomats, as few of the most high-profile posts can be filled by foreign service officers.

He added there are aspects of diplomacy that political appointees have not been able to do, especially those with less understanding of global governance and the geopolitical reality on the ground. He also said political appointees are unaware of the demands associated with diplomatic posts.

“Political appointees won’t be able to carry these kinds of discussions,” Mr. Saint-Jacques said. “The value of an ambassador is your capacity to network and to be a good networker you have to be knowledgable.”

He said that when picking the replacement for Mr. McCallum, he urged the government to pick a career diplomat for the Beijing post. Mr. McCallum resigned after comments he made that were out of step with the messaging of the Canadian government on the extradition hearing of Huawei executive Meng Wanzhou.

Although Mr. Rae has lots of good qualities, Mr. Saint-Jacques said he isn’t trained as a diplomat.

A spokesperson for Foreign Affairs Minister François-Philippe Champagne (Saint-Maurice-Champlain, Que.) said Mr. Rae has “dedicated his life to serving Canadians and has done crucial work as Canada’s special envoy to Myanmar and Canada’s special envoy on humanitarian and refugee issues.”

Syrine Khoury said Mr. Rae will “continue to strengthen Canada’s presence at the UN and on the world stage,” adding that the selection of ambassadors is based on their “vast and varied experience,” and the political appointees are “highly qualified individuals who bring a unique set of skills and knowledge in line with our foreign policy objectives.”

A Liberal source told The Hill Times on background that it’s important political appointees have a wide-range of experience and skills beyond being diplomats, citing Mr. Blanchard’s work in the private sector being helpful at the UN on developmental funding.

The source said it is important to have vast experience, including backgrounds in politics and business, in order to send countries around the world a message that diplomacy is important to Canada.

The use of political appointees for diplomatic posts has been a tradition in Canadian diplomacy which intensified under former prime minister Brian Mulroney and continued with successive governments. Past prime minister Stephen Harper raised eyebrows for appointing Toronto lawyer Vivian Bercovici as ambassador to Israel, Bruno Saccomani—who previously was the head of his RCMP security detail—as envoy to Jordan, former House of Commons Sergeant-at-Arms Kevin Vickers as ambassador to Ireland, and defeated former foreign affairs minister Lawrence Cannon as envoy to France.

Mr. Trudeau selected Kirsten Hillman, a career diplomat, as Canada’s ambassador to the U.S. She is the first career diplomat in the post since Michael Kergin held the role from 2000 to 2005.

Former diplomat Gilles Rivard, president of the Retired Heads of Mission Association, said when a political appointee gets a top job, there is always a question if a career diplomat would be better suited to handle the post.

But in the case of Mr. Rae, he said, he already has some experience on the world stage in his special envoy roles. Mr. Rae was a former NDP premier of Ontario and the interim federal Liberal leader from 2011 to 2013.

Mr. Rivard, a former deputy permanent representative to the UN and ambassador to Haiti, said the danger of selecting political appointees is seen in the case of Mr. McCallum.

He said more and more political appointees will be discouraging for those in the foreign service who want to hold those positions.

“It’s obvious that it affects the morale of people,” he said.

The head of the union representing foreign service officers said there is a recognition that it is the government’s prerogative to appoint the people it wants.

Professional Association of Foreign Service Officers (PAFSO) president Pamela Isfeld said there is a recognition that there are political appointees that bring a distinct set of skills to some appointments like the ambassador to the U.S. and the UN, noting there is a close co-operation with the foreign service.

Ms. Isfeld said the concern is when political appointees are selected to lead much smaller missions.

“The person then starts to have less of a support staff to help them,” she said, adding that in general the existing professional foreign service should be the “first port of call” when looking to fill diplomatic posts.

The appointment of Mr. Rae, Ms. Isfeld said, carries on the acceptable tradition of political appointees and has a lot of support within PAFSO.

Former diplomat Colin Robertson, a past PAFSO president, said there are cases where a political appointee makes the most sense, adding that in Washington, D.C., having a political appointee in the role gave Canada greater access.

Although Mr. Harper appointed career diplomats to the UN post, Mr. Robertson said the appointments of Mr. Blanchard and Mr. Rae shows the added emphasis that Mr. Trudeau places on the UN, adding that sending his Mr. Rae to New York City shows that Canada is still “quite serious” about the UN despite the unsuccessful Security Council election.

Canadian International Council president Ben Rowswell, a former Canadian ambassador to Venezuela, said in email that the disadvantage in appointing career diplomats is that the foreign service generates “uniformity in thinking.”

“The best ambassadors are independent thinkers who can speak directly to a prime minister and influence his decisions,” he said, adding that is why Mr. Rae is the “best person” for the UN job.

“He has more than 20 years of work in international affairs on issues ranging from terrorism, federalism, and human rights—but importantly, he led this work as an independent actor, coming up with his own judgements on the application of Canada’s interests. That makes his perspective even more valuable than someone who has been in the system for decades.”

He added that the foreign service needs a change to reward “innovation and new thinking.”

Conservative MP Stephanie Kusie (Calgary Midnapore, Alta.), who served as Canada’s chargée d’affaires in El Salvador and was a policy adviser to then-minister of state for Foreign Affairs for the Americas Peter Kent (Thornhill, Ont.), said there are “pros and cons” for both the selection of political appointees and career diplomats.

“You can get good people out of both systems, and you can get bad people out of both systems,” she said.

She said while political appointees don’t always know the practices of the foreign service, they do know government policies in depth and know the prime minister and foreign affairs minister.

In her time in the foreign service, Ms. Kusie said she saw the same high-level people being recycled over again for various heads of missions.

“It’s frustrating and demoralizing for lower people that want the opportunity to serve at a higher capacity,” she said, adding that another issue is the tight rules that diplomats are restricted to in creating policy and speaking to the media.

“The golden ticket isn’t always foreign service officers, because in a way it is its own political party, promoting the same people,” Ms. Kusie said. “It’s good to have a healthy mixture of both as long as they are intelligent, [have] good judgement, and are courageous to implement the political ideology, but tactful in doing that.”

Independent Senator Peter Boehm (Ontario), a former career diplomat who served as ambassador to Germany and was Mr. Trudeau’s G7 sherpa, said the selection of political appointees is cyclical.

“If you want to have a head of mission who is plugged in to the centre to the PMO and the PCO, you’ll go with a political appointee if it makes sense to do so,” he said.

He said the Canadian system is nothing compared to the one the U.S. has, where a large number of its ambassadors around the world are large political donors.

Sen. Boehm said Mr. Rae is “cut out” for multilateral work, adding that some on the political side have that capability, comparing him to past UN ambassador and former Ontario NDP leader Stephen Lewis.