Canada is not at war with ISIS, but security and intelligence forces need special powers to fight the "sophisticated" terror group, says the outgoing security adviser to the prime minister.

Richard Fadden, who announced his retirement last week after nearly 40 years of public service, told CBC Radio's As It Happens that ISIS does not pose an "existential" threat to Canada, but it is accomplishing its prime objective of breeding terror.

Military personnel deployed in Syria and Iraq may feel like they are fighting a war, but Fadden said that is not the perspective of Canada's security intelligence agencies.

"I think people would think we are fighting a very, very serious situation that requires a great deal of attention and probably some new powers and resources. But I think most of my colleagues would say no, it wasn't war," Fadden told host Carol Off.

Prime Minister Justin Trudeau has faced sharp criticism for similarly rejecting the label "war." He said the word suggests the fight can be won by one side or the other, and in this case there is no path for ISIS to win against the West.

Richard Fadden reflects on his career in national defence and intelligence gathering after announcing his retirement 21:29

Fadden added that constitutionally a war is formally declared by the Queen or her representative, the Governor General.

Urges 'calm discussion'

But no matter what the conflict is called, Fadden urged "calm discussion" around new anti-terror laws that were brought in under the previous Conservative government to fight groups like ISIS. In the past, Fadden said, polarized debate has been fuelled in the wake of a crisis by hyper-partisans, "gotcha" media and academics who are better versed in theory than in practical solutions.

"Do I like the idea as a Canadian citizen that instrumentalities of the state have powers that could affect me? No, I do not," he said. "But we are facing international terrorism threats of the sort we have not faced before, and Parliament has decided it needs some extreme tools."

Fadden said he does not have to personally agree or disagree with the direction of the government, but he would have quit if he believed Bill C-51 had crossed the line.

"If I had felt very strongly that something in that statute was unconstitutional, unlawful or unacceptable, I would have done what I think any public servant would have done. I would have resigned," he said. "But I was still there."

Public and political debate over the new terror law continues, and the Liberals have promised to repeal "problematic" elements of the law.

New powers used

Last month, CSIS director Michel Coulombe revealed that agents have used new powers to disrupt suspected terrorist threats nearly two dozen times since last fall.

In the wide-reaching interview, Fadden also said he does not believe the fast-tracked process to bring 25,000 Syrian refugees into Canada presented significant security risks, because equivalent checks were put in place.

"Is bringing in 25,000 new people having no effect on terrorism? I wouldn't say so, but I think every reasonable step was taken to ensure that the threat was kept to a bare minimum," he said.

The interview with Richard Fadden airs on CBC Radio's As It Happens at 6:30 p.m. local time, 7 p.m. in Newfoundland.