OTTAWA - History will face off against national security this week in a court battle over decades-old intelligence files on socialist icon Tommy Douglas.

The case pits the right of Canadians to see historically significant information against the government's determination to protect the secrets of the spy trade.

Arguments are to be heard Wednesday in Federal Court.

The Canadian Press is challenging the federal government's refusal to fully disclose a 1,142-page dossier on Douglas, a former Saskatchewan premier and federal NDP leader who is widely hailed as the father of medicare. The file was amassed by the RCMP from the late 1930s until shortly before Douglas's death in 1986.

Paul Champ, lawyer for The Canadian Press, said the case is about more than gaining access to historical material on Douglas, whom he said "played a significant role in shaping Canadian society today."

"The greater precedential impact of this case relates to when and how Canadians can access important historical documents and to what extent can our security intelligence branches try to sit on information indefinitely."

The battle dates back to 2005, when reporter Jim Bronskill of The Canadian Press requested the Douglas file under the Access to Information Act.

Library and Archives Canada, which is currently in possession of the Douglas dossier, initially released over 400 pages, some of them heavily censored. The agency maintained fuller disclosure would jeopardize the country's ability to detect, prevent or suppress "subversive or hostile activities."

It was acting on the advice of the Canadian Security Intelligence Service, which took over responsibility for domestic security investigations from the RCMP in 1984.

Bronskill launched a court challenge in 2009 after the federal information commissioner agreed with the government that most of the dossier should be kept under wraps.

In a closed-door hearing late last year, Judge Simon Noel expressed concern that Library and Archives had not paid sufficient attention to its mandate as the keeper of the country's history. In response, the agency released portions of more than 300 additional pages from the Douglas file last week.

However, more than one-third of the pages in the file remain totally blacked out.

The uncensored material shows RCMP security officers shadowed Douglas for four decades, attending his speeches and eavesdropping on his conversations. They were particularly interested in the erstwhile Prairie preacher's links to the peace movement and members of the Communist party.

The newly disclosed pages show the RCMP compiled information on talks between Douglas and actress Jane Fonda in 1970 on halting the Vietnam War. The Mounties were also interested in efforts to create the New Democratic Party in the early 1960s, appearing to equate the fledgling movement with the Communist party.

Douglas' daughter, actress Shirley Douglas, and the Canadian Historical Association, have filed affidavits supporting full disclosure of the file.

However, CSIS has argued vehemently against uncensored release of the information. In an affidavit, the agency's access-to-information co-ordinator, Nicole Jalbert, has maintained full disclosure could risk the lives of confidential informants and compromise the agency's ability to conduct secret surveillance.

She has said secrecy is vital for any files containing names of sources or intelligence agents, even if they're long dead, or offering a glimpse of how security agencies conduct their business. She has said such files should remain secret "maybe longer" than 100 years, although "perhaps not forever."

"The requirement for secrecy with respect to past and current activities of a security intelligence agency is essential," according to Jalbert. "The origin of information, its extent and the methods by which it was obtained must remain secret."

However, Champ said such indefinite secrecy is antithetical to democracy.

"Intelligence agencies see their work as somehow exceptional, that only they should ever be allowed to see what they do. I don't think they understand or truly grasp that secrecy is the exception in a democracy," Champ said.

"We tolerate it because we do recognize that during periods of crisis and emergencies it's important for security. But we need to be vigilant that the tendencies of these intelligence branches don't obscure the actions of our government."

At a news conference in Vancouver on Monday, Prime Minister Stephen Harper emphasized that politicians play no role in determining whether security-related files should be released.

"Those kinds of decisions are made not by political people, not by political staff. They're made by government lawyers who determine under the act what kind of information can be released to the public."