A move by telecommunications firms to be more forthcoming with the public about their role in police and spy surveillance could divulge "sensitive operational details," a senior Public Safety official warned in a classified memo.

Company efforts to reveal more about police and intelligence requests — even the disclosure of broad numbers — would require "extensive consultations with all relevant stakeholders," wrote Lynda Clairmont, senior assistant deputy minister for national and cybersecurity.

Clairmont's note, released under the Access to Information Act, provided advice to deputy minister Francois Guimont on the eve of his one-hour April 17 meeting with representatives of Telus Corp. to discuss specifically what information the company was allowed to tell the public about electronic surveillance activities.

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Telus released a so-called "transparency report" five months later, revealing it had received more than 103,000 official requests for information about subscribers in 2013.

Rogers Communications published a similar report in June — three months before Telus — becoming the first of the major Canadian telecom firms to issue one. Bell Canada, the other major company, has yet to release a report.

The internal Public Safety memo sheds new light on behind-the-scenes tensions between government officials and industry amid pressure from privacy advocates and civil libertarians for details of the scope and nature of law enforcement access to Canadians' subscriber information, phone calls and email messages.

The demand for more transparency was fuelled by leaks from former American intelligence contractor Edward Snowden, whose significant disclosures revealed the U.S. National Security Agency had access to a huge volume of telecommunications data.

The revelations prompted a flurry of questions about the activities of the NSA's Canadian counterpart, the Communications Security Establishment, as well as the Canadian Security Intelligence Service and the RCMP.

The Public Safety Department is committed to protecting the security of Canadians while respecting their privacy, Clairmont wrote in her April 16 memo to Guimont, stamped "Secret/Canadian Eyes Only."

"We recognize that transparency is key to giving Parliament and Canadians confidence in our ability to meet both these objectives, but must continue to ensure that sensitive operational details remain protected."

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There was a need to evaluate whether such details could be revealed even through "mass aggregate reporting of data," she added.

A month before Telus's scheduled meeting with Guimont, the company said it was prohibited from disclosing certain information by a governing document known as "Solicitor General's Enforcement Standards for Lawful Interception of Telecommunications."

In a letter to Christopher Parsons of the University of Toronto's Citizen Lab, a digital rights body, Telus privacy officer Heather Hawley said the company would ask the government to "clarify and limit the scope of current confidentiality requirements and to consider measures to facilitate greater transparency."

Neither Telus and Public Safety would make anyone available to answer questions about their discussions.

Rogers spokesman Kevin Spafford said the company did not talk with the government about its June transparency report before it was published.

The report said Rogers received almost 175,000 requests for customer information from government and police agencies last year. Of those, 74,415 were made under a warrant or court order, including production orders, summons, subpoenas and search warrants issued by a judge or other judicial officer.

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In deciding what to disclose in its transparency report, the company abided by just one restriction, Ken Engelhart, chief privacy officer for Rogers, said at the time.

"The only legal restraint is that you can't even give a number of wireless interceptions that you do — that's like a wiretap, but it's a wireless tap," Engelhart said in an interview.

It was important to get a transparency report out, he continued.

"I'm hopeful it won't bother the law enforcement people, but if it does, we thought that the needs of our customers came first."