Ottawa is stating it did not spy or facilitate any snooping on Canadian soil during the G20 summit in Toronto, while refusing to offer a clear denial of any co-operation with foreign allies to intercept communications at the 2010 meeting.

Reports that the U.S.-based National Security Agency was active in Canada at the time of the meeting of world leaders has renewed calls for greater scrutiny of its domestic counterpart, the Communications Security Establishment Canada.

Newly released NSA documents, leaked by former contractor Edward Snowden and published by the CBC on Wednesday, say the American agency's operations during the 2010 summit were "closely co-ordinated with the Canadian partner."

Story continues below advertisement

However, both CSEC and the federal government refused to explain Canada's role in the monitoring of communications at the time, and whether the targets of the American operation were world leaders, anti-globalization demonstrators or anyone else.

CSEC chief John Forster limited his comments to explaining his agency's legal mandate, which prevents it from conducting broad monitoring operations on Canadian soil.

"I cannot ask or perform activities on behalf of our partners that are against the law in Canada. I would not do that, our agency would not do that, it is against the law," Mr. Forster told reporters after a committee meeting on Parliament Hill.

Defence Minister Rob Nicholson defended CSEC, stating its operations are supervised by an independent commissioner, Jean-Pierre Plouffe.

"That independent commissioner has indicated, for the last 16 years, that CSEC has complied with all Canadian laws," Mr. Nicholson said.

However, NDP Leader Thomas Mulcair raised the possibility during Question Period that Canada used the NSA "to illegally spy on Canadians."

The NDP is calling for CSEC to operate with greater oversight, such as the five-member committee of prominent Canadians that supervises the activities of the Canadian Security Intelligence Service (CSIS).

Story continues below advertisement

"The question is: Who's providing the oversight? And in this case, it's clear there is not appropriate oversight," NDP MP Paul Dewar said. "I'm sorry, but when it comes to something as sensitive as CSIS and CSEC, it's not good enough [for the government] to say, 'Trust us, we've got this in hand.' "

Craig Forcese, a University of Ottawa professor of law, said the leak is "tantalizing," while stating that more information is needed on the actual operations.

"Spies spy. The question is whether in the course of their spying, they are acting in accordance with the rules that govern spying ," Mr. Forcese said in an interview, after posting a lengthy entry on his blog on this issue on Thursday.

Many leaks about classified NSA spying programs have come from Mr. Snowden, the former U.S. intelligence contractor who now faces espionage charges in the United States while he lives in Russia. Other secret CSEC intelligence programs highlighted in the past six months include:

An effort to help allied agencies spy on diplomats’ BlackBerrys during the 2009 G20 summit in London;

The continuing use of Canadian embassies in unspecified foreign countries as listening posts;

A 2012 CSEC effort to data-mine telecommunications traffic from Brazil’s Ministry of Mines and Energy, around the same time the NSA was spying on that country’s leaders and energy sector.

The Snowden revelations have confirmed that the world's intelligence-gathering agencies are particularly active in monitoring communications during international summits and meetings. Diplomats and other government officials know to be watchful of what they say and write on various devices, especially at such events, experts said.