A former top national security adviser says that during his career leaks of classified information at National Defence prompted him to call in the RCMP "a couple of times" in recent years.

Richard Fadden, who served as head of the Canadian Security Intelligence Service, deputy minister of defence and national security adviser to two prime ministers, says he never thought that top secret information was being allowed to slip.

But lower grades of classified records and data ending up in the media — or in another public domain — was a continuing irritation, Fadden told CBC News in a recent interview.

"Over the course of my career, I've either asked for or ordered a number of [RCMP] inquiries to be made when classified information has been leaked," said Fadden. "It is almost impossible to find who does it."

He would only say he took the extraordinary step "a couple of times over the course of the last five or six years, but none of it was very high level" information.

Admiral investigated

Fadden was quick to put distance between his remarks and the current RCMP probe into the military's second highest-ranking officer, Vice-Admiral Mark Norman, who was temporarily relieved of duty on Jan. 13 without explanation.

The Liberal government, National Defence and the RCMP have all refused comment, but a number of sources have said the federal police service is investigating Norman for a leak of classified information, possibly involving the shipbuilding program.

Vice-Admiral Mark Norman was temporarily relieved of his duties as vice-chief of the defence staff last month. The government has been tight-lipped about Norman's removal, though sources have said it involves a leak of classified information. (CBC)

"I think that's under investigation. I don't know a great deal about it. So, I am going to decline to answer," Fadden said when asked about the Norman case.

The silence on the investigation has been unusual, particularly since it involves one of the most senior, sensitive jobs in the Canadian military.

RCMP Commissioner Bob Paulson has refused to comment, but will appear before the Senate security and defence committee on Monday.

Previous navy leaks

Some of the investigations that may have been ordered on Fadden's watch include inquiries made by the RCMP, during late 2015, into how the media got hold of a federal cabinet decision that temporarily halted plans to lease a new military supply ship. CBC News and The Canadian Press both reported that story.

Two weeks ago, CBC News reported that the Mounties also probed a 2014 leak about the former Conservative government's decision to sole-source the $800-million purchase of new Sea Sparrow missiles for the frigates. That 2014 story was reported by Postmedia.

There has been speculation that the investigation into Norman is part of a wider-ranging attempt to plug leaks at the Defence Department.

Fadden said that in his experience many large departments have chatty people.

"I think, in any organization that has more than 50,000 people, it is almost impossible for information to be kept entirely secret," he said.

"So I come back to the point, it depends on what kind of information you're talking about. I really had no worries when I was [national security adviser] or when I was deputy at defence about top secret information, really core information being let out."

Different levels of secrecy

Fadden underlined the distinction between top secret, classified and protected information, the different levels of government secrets.

Those levels were blurred under the former Conservative government and continue to be hazy under the current Liberal administration.

Under former prime minister Stephen Harper, the definition of what could be considered secret cabinet information was expanded through regulations rewritten by the federal Treasury Board in 2013.

Departmental lawyers were given wider discretion to decide what constitutes a cabinet secret — known as a "confidence."

The result has been that data — previously considered innocuous — was labelled a state secret and hidden not only from the public, but from members of Parliament, parliamentary watchdogs and even the information commissioner.

Fadden tacitly acknowledged the confusion and said he always looked at the contents of the leak and where it ended up.

"You go down two or three levels [of classification] and you know, you're starting to deal with the private sector, and it's not always clear what's classified and what isn't."