Former prime minister Joe Clark says current PM Stephen Harper needs to "bring people into the facts" and tell the real story about what went on with Senator Mike Duffy and Nigel Wright, the PM's former chief of staff.

Clark has written a new book — titled How We Lead — about Canada's foreign policy, and our country's global standing. The book is quite critical about Harper's approach to international affairs.

CBC chief correspondent Peter Mansbridge interviewed Clark on Wednesday about leadership, not only on foreign affairs, but also on management, including how he sees the Senate scandal that's been unfolding in Ottawa.

See the full interview with former prime minister Joe Clark on Mansbridge One on One this weekend Saturday

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Clark says Harper should get some advice about how to tell the story effectively.

PM: "As unlikely as it may seem, if Stephen Harper picked up the phone and called you up and said, 'I need your advice,' what would be the single piece of advice you'd give him on what was happening right now?"

JC: Right now, I think he has to bring people into the facts. That's a careful way of saying…"

PM: "It's a careful way of saying he's not telling us the real story."

JC: "And I think he needs to tell the real story and I think he needs to seek some advice as to what's the most effective way to do that....That's a question he should have asked a long time ago."

Clark also says that what really surprises him is that the party is attacking its own.

"It raises a very real question that comes back to the prime minister: if Mike Duffy has been such a problem, who appointed him? If Nigel Wright is the person they're blaming, who hired him?"

"This is very tricky ground for the prime minister and he, I think, is trapped by a process, by a use of a process that he himself created," Clark says.