Opposition MPs say the government has to do more to reassure Canadians after a document newly released by former NSA contractor Edward Snowden suggested Canada's communications spy agency tracked people through free airport Wi-Fi.

The top secret document shows Canada's electronic spy agency used information from the free internet service at a major Canadian airport to track the wireless devices of thousands of ordinary airline passengers for days after they left the terminal.

Under repeated questioning by opposition MPs on Friday, Defence Minister Rob Nicholson didn't directly deny the story, but said that the document detailing work by the Communications Security Establishment Canada (CSEC) doesn't show that Canadian communications were targeted or used.

New Democrat House Leader Nathan Cullen said the government needs to offer proof no Canadians were tracked.

"All we saw in the House today was rhetoric and empty lines. Talking points aren't going to assure Canadians that they are not in fact being spied upon by their government," Cullen said.

"We see quotation [marks] and weasel-words from the minister. This is worrisome for me and it certainly doesn't give any assurance to Canadians who are properly worried as well."

Nicholson says CSEC "made it clear to CBC that nothing in the documents that they had obtained showed that Canadian communications were targeted, collected, or used, nor that travellers' movements were tracked."

The spy agency is supposed to be collecting primarily foreign intelligence by intercepting overseas phone and internet traffic, and is prohibited by law from targeting Canadians or anyone in Canada without a judicial warrant.

More CSEC debate next week

The Liberal Party moved to continue debate on Tuesday, planning to devote a day to debating the spy agency's activity. Liberal MP Wayne Easter will move that the government "immediately order CSEC to cease" all illegal monitoring of Canadians and "increase proper oversight" through a committee of parliamentarians.

The non-binding motion will be debated as part of a regularly scheduled opposition day in which one of the non-governing parties controls the day's agenda.

That debate will come the day after senators on the national security and defence committee have a chance to question John Forster, CSEC's chief, as well as Prime Minister Stephen Harper's national security adviser, Stephen Rigby, and Michel Coulombe, director of the Canadian Security Intelligence Service.

Three consumer and privacy groups wrote to Daniel Lang, the committee's Conservative chair, on Friday to ask that he have the three experts testify under oath.

“It is vital to get to the bottom of what our intelligence agencies are doing in terms of mass surveillance of Canadians contrary to the law," Vincent Gogolek wrote on behalf of the B.C. Freedom of Information and Privacy Association, Open Media and the Canadian Internet and Public Interest Clinic.

"Your committee has the first opportunity to ask these questions, and we believe the gravity of this fact-finding exercise must be impressed on your witnesses. As such, we ask that testimony from these officials scheduled for Monday, Feb. 3, 2014, occur under oath.”

Metadata at issue

The latest Snowden document indicates the spy service was provided with information captured from unsuspecting travellers' wireless devices by the airport's free Wi-Fi system over a two-week period.​ In the case of the airport tracking operation, that information came from metadata that apparently identified travellers' wireless devices, but not the content of calls made or emails sent from them.

New Democrat MP David Christopherson asked Nicholson to categorically deny the agency has tracked Canadians, but Nicholson would only say that regular reports by a watchdog, the CSEC commissioner, affirm the signals intelligence agency doesn't break the law.

Nicholson declined to be interviewed by CBC News following question period.

Nicholson's argument seemed to hinge on a difference in terminology, referring to communications rather than metadata.

Metadata reveals a trove of information including, for example, the location and telephone numbers of all calls a person makes and receives — but not the content of the call, which would legally be considered a private communication and cannot be intercepted without a warrant.

Charmaine Borg, the NDP's digital issues critic, zeroed in on the question of metadata and their distinction from a person's conversations.

"Is the government really claiming that gathering information is not the same as illegally tracking Canadians?" she said.

Nicholson repeated that nothing in the document "showed that Canadians' communications were targeted, collected or used, nor that travellers' movements were tracked.​"

Value of intelligence vs. privacy

CSEC itself referred to the metadata around a person's communications, which it is legally authorized to collect and analyze as part of its role in gathering foreign intelligence.

"Metadata is technical information used to route communications, and not the contents of a communication," CSEC said in a written statement.

Metadata is "the new frontier of signals intelligence operations around the world," said Wesley Wark, an expert on national security and visiting professor at the University of Ottawa.

Wark says metadata is valuable because intelligence agencies can trace the networks through which communications flow and identify patterns and people they may be concerned about.

"You don't actually have to read the content of communications if you can follow the networks' signalling and patterns and movements involved as people move from place to place with their wireless devices and so on, and you still have an important intelligence tool," Wark said.

"Many voices have said there's not really any significant intelligence payoff that could be measured in the balance against the potential intrusions to civil liberties and privacy."

Liberal MP Scott Brison said MPs spend a lot of time in airports and questioned whether the government would tell any MPs or other Canadians whether they had been caught up "in this data sweep."

"And will the minister initiate his own investigation into CSEC's activities to reassure Canadians that their privacy has not been violated?"

Nicholson didn't answer the question.

Interim Privacy Commissioner Chantal Bernier says privacy is a fundamental right and that privacy law needs to be modernized to address concepts like metadata.

"People do not want to be tracked. People do not believe that their metadata is innocuous," Bernier told CBC News.

Mobile users click here to read the CSEC statement.