Brian Mulroney has a blunt warning for Stephen Harper: His government is reaching the point when Canadians want change and the platforms of his competition simply won't matter.

The current Prime Minister will soon pass Mr. Mulroney to become the sixth-longest-serving prime minister in Canadian history and Mr. Mulroney notes that political longevity comes with obvious risks.

The former Tory prime minister who led the country for nearly nine years from 1984 to 1993 has been in the media this week to discuss the 30th anniversary of his landslide electoral victory. But in an interview with CTV's Power Play, Mr. Mulroney weighed in on the current political landscape with polls consistently showing the Conservatives trailing the Liberals.

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At a certain point, Mr. Mulroney said it won't matter that Liberal Leader Justin Trudeau is accused of not offering much in terms of policy.

"His program is that he's not Stephen Harper," said Mr. Mulroney, who says he continues to support the Harper government. "When I ran in '84... I won because I wasn't Pierre Trudeau and then Jean Chrétien 10 years later won because he wasn't Brian Mulroney. So it's part of a desire for change, which is normal, and so I think it's going to make for a great election [in 2015]."

The next federal election is scheduled for Oct. 19, 2015, according to the country's fixed-date election law.

Mr. Mulroney said Mr. Trudeau is a much stronger opponent for Mr. Harper than the last two Liberal leaders he faced: Stephane Dion and Michael Ignatieff. However, the former prime minister also spoke highly of NDP Leader Thomas Mulcair.

"Not to exclude Mr. Mulcair by the way, whom I happen to view as the best opposition leader since John Diefenbaker and I've known them all and seen them all. And so the idea that this is going to be a two-party tap dance [is] wrong," he said.

Mr. Mulroney also weighed in on whether the government should call an inquiry into the issue of murdered and missing aboriginal women in Canada. Aboriginal leaders and opposition parties are calling for such an approach, but Mr. Harper has rejected the idea.

"I can see both sides. Let's go this way rather than that," Mr. Mulroney told CTV's Power Play. "But if I were there, I wouldn't hesitate. I would have a royal commission into aboriginal issues of this kind because of the sensitivity and the importance to aboriginal peoples at this particular time in their evolution."