OTTAWA -- A secret spy service file on Pierre Trudeau came close to eluding destruction 30 years ago, newly disclosed memos reveal.

However, a late October 1988 recommendation that the dossier on the former prime minister be preserved for at least another decade was nixed just days later, sealing its fate.

The Canadian Press reported last month that the Canadian Security Intelligence Service scrapped the Cold War file on Trudeau in 1989 instead of sending it to the national archives.

The Trudeau dossier was among hundreds of thousands of files on a wide array of groups and individuals the newly formed CSIS inherited in the 1980s after the RCMP Security Service was disbanded following a series of scandals.

CSIS said the file on Trudeau was destroyed because it fell short of the threshold for retention by either the service or the archives.

The news rankled leading historians, who said an intelligence file on a prime minister should be kept without hesitation given its significance to the national public record.

Though the contents of the Trudeau file are a mystery, the RCMP might have noted the future prime minister's support of striking asbestos miners in Quebec or his exotic travels, including a visit to the Soviet Union in the early 1950s.

Trudeau, Canada's third-longest-serving prime minister, left office in 1984 and died in 2000.

Internal CSIS documents, released this month under the Access to Information Act, shed additional light on how the decision to destroy the Trudeau file was made.

The intelligence service possessed files on people suspected of being subversives, spies or terrorists, as well as those who underwent security screening requested by foreign countries, required domestic security clearances or might have encountered a foreign intelligence service while travelling.

Reviewers who combed through the files in the late 1980s used general criteria to determine whether a file had archival value when no longer needed for operational reasons. They considered whether the material involved:

unusual or important cases or events;

investigations employing exceptional techniques or methods;

legal opinions relating to cases;

information exchanged with another agency;

information used or prepared for judicial proceedings;

internal disciplinary matters; or

information obliged by law to be retained.

A newly declassified memo of Oct. 24, 1988, about the Trudeau file noted he "could be the object of future threats or acts of violence" given his high profile, or he might be the subject of threat-assessment requests from allied agencies when going abroad -- that is, that Trudeau's file might be useful for understanding how best to protect him.

The unnamed reviewer therefore recommended the file "be retained for a further period of 10 years for VIP security related purposes."

"File to be again reviewed and assessed at that time to establish if further required or otherwise."

A memo dated two days later, in what appears to be the same handwriting, said there was no "investigational requirement" related to the material, adding: "File does not fall within archival criteria. Recommend file be destroyed."

Added another official: "Recommendation agreed with."

Reid Morden, CSIS's director at the time, says he stayed out of the decision-making. He doesn't recall being told of a file on Trudeau or other prominent politicians.

"It's the sort of thing you do remember," Morden said in an interview.

It has been known for years that old security files on former prime ministers John Diefenbaker and Lester Pearson were also purged from the CSIS holdings. The Diefenbaker, Pearson and Trudeau files were all destroyed on Jan. 30, 1989, the newly released memos say.

According to Morden, "If the archives had said, 'We want to keep that,' the outcome would have been different."

The U.S. Federal Bureau of Investigation, which worked closely with the RCMP security service, had a file on Pearson consisting of innuendo and hearsay but no evidence of Communist ties.

A Nov. 1, 1988, CSIS note recommending destruction of the Pearson dossier says: "Nothing significant on file that isn't covered in some published newspaper account."

Some files -- including lengthy ones on Quebec premier Rene Levesque and NDP leaders David Lewis and Tommy Douglas -- wound up in the national archives.

An Oct. 25, 1988, memo on the Lewis file says there is "no clear requirement" to forward the material to the archives, but notes it contains documents of "particular interest," including a 1939 speech at Ottawa's Chateau Laurier hotel when Lewis was a young leader in the Co-operative Commonwealth Federation.

"The nature of the information (particularly in the early volumes) is such that I would recommend the file be sent to Archives."