Canada’s electronic spy agency is defending its espionage activities against countries around the world, including trading partners — often at the request of the U.S. — as necessary to support government decision-making and provide a better understanding of global events.

The statement came in response to questions that CBC News posed to the Communications Security Establishment Canada (CSEC), the little-known spy service that collects intelligence by intercepting mainly foreign communications and hacking into computer data systems.

CBC News reported Monday that a top secret document retrieved by American whistleblower Edward Snowden reveals Canada has set up covert spying posts at the request of the giant U.S. National Security Agency, and is involved in joint espionage operations with the NSA in about 20 countries.

CSEC says it has a "mandate to intercept foreign communications signals to respond to government of Canada priorities."

The agency says it collects foreign intelligence "to protect Canadians from threats, and we take that responsibility very seriously."

It is not clear in either the leaked Snowden document or CSEC’s response to it, what kind of threats Canada faces that would require it to conduct espionage against 20 countries, including some of its important trading partners.

The secret document reveals that Canada has undertaken spying operations in countries that are “unavailable” to the NSA, as well as setting up listening posts "at the request" of the U.S. agency.

CBC News asked CSEC whether it does whatever the NSA asks it to do.

The agency replied that its activities respond only to the priorities of the Canadian government, "many of which are common to our allies."

All of this sparked some heated questions for the Harper government in the House of Commons today.

NDP MP Jack Harris demanded to know whether the government would implement some form of parliamentary oversight of the spy service in light of the CBC News report.

Defence Minister Rob Nicholson, who is responsible for CSEC, pointed out only that the operations of the intelligence service are already reviewed by an oversight commissioner.

That commissioner reports to Nicholson.