Open this photo in gallery Peter MacKay speaks before Conservative leader Andrew Scheer arrives at a campaign stop in Little Harbour, N.S. on Oct. 17, 2019. Adrian Wyld/The Canadian Press

Former U.S. president Barack Obama’s decision to endorse Liberal Leader Justin Trudeau is “inappropriate,” says former Conservative cabinet minister Peter MacKay.

Mr. MacKay, who spoke to reporters on Thursday evening outside of an event for Conservative Leader Andrew Scheer in Little Harbour, N.S., said he has always been of the view that one does not “interfere in foreign elections.”

“I’m not just talking about hacking,” he said.

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“You just don’t comment; you don’t get drawn into the debate, especially in the dying days of a campaign. I think it’s a desperation move. It’s a Hail Mary, and it’s not going to make a difference.”

On Wednesday, Mr. Obama tweeted his support for Mr. Trudeau, saying he was proud to work with the Liberal Leader.

“He’s a hard-working, effective leader who takes on big issues like climate change,” Mr. Obama wrote.

“The world needs his progressive leadership now, and I hope our neighbours to the north support him for another term.”

In response to the endorsement, Mr. Scheer was careful with his words in Ancaster, Ont., on Wednesday, saying he is not interested in what former foreign leaders are saying.

Mr. Scheer also declined to say whether he thought it was appropriate for Mr. Obama to weigh in on the Canadian election.

“I’ll let Canadians be the judge of that,” he said Wednesday. “I’m just focusing on finishing this campaign strong, earning the trust of Canadians to put forward our plan to help them get ahead.”

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Mr. MacKay, who is not running in this election, went much further than Mr. Scheer, adding that he believes the endorsement was “entirely orchestrated” by the Liberals.

“I’m convinced,” he said. “It is not appropriate. Period.”

Earlier this year, former Conservative prime minister Stephen Harper posted his support for Narendra Modi on Twitter.

“For India to realize its potential, it needs the courageous & visionary leadership of Prime Minister Modi,” Mr. Harper wrote. “Proud to stand with him.”

Speaking on the campaign trail on Thursday, Mr. Trudeau avoided directly answering questions about whether Mr. Obama was asked to endorse him just days before Canadians head to the polls.

“I was obviously happy to hear his words yesterday, but nobody tells Barack Obama what he should do,” he said in Trois-Rivières, Que. “Barack Obama makes up his own mind.”

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Mr. Trudeau also said the last time he spoke to Mr. Obama was in the spring when he came to Ottawa.

“We talked about how we’re going to continue to fight for things that matter for people around the world, like the fight against climate change,” he said.

Mr. Obama was president of the United States from 2009 to 2017. He also endorsed Emmanuel Macron for president in France’s 2017 election.

Former Canadian ambassador to the United Nations Paul Heinbecker has said he didn’t think there was any impropriety in Mr. Obama’s endorsement.

“I don’t think it’s unfair, just unorthodox," Mr. Heinbecker said Wednesday.

With reports from Michelle Zilio and Marieke Walsh