OTTAWA - As the Liberals prepare to bolster a review of national spy services, two federal security agencies have flagged serious headaches that might come with more scrutiny, internal documents show.

The RCMP fears more eyes looking over its shoulder could compromise criminal investigations, while the electronic spies at the Communications Security Establishment warn against creating a super-watchdog with its associated "burden and costs," say notes obtained under the Access to Information Act.

The Trudeau government plans to usher in a national security committee of parliamentarians, whose members would have access to classified records.

It is also studying gaps in the current web of watchdogs that monitor intelligence services to ensure a comprehensive system is in place.

Existing review bodies cannot look at issues beyond their specific agency of focus, and have "limited authority" to collaborate with one another, say briefing notes prepared for Public Safety Minister Ralph Goodale.

It means the Civilian Review and Complaints Commission, which oversees the RCMP's national security activities, might be barred from exchanging notes on an alleged scandal with the watchdog that keeps an eye on the Communications Security Establishment.

The Liberals are looking at fostering such co-operation - known as inter-agency review - because many watchdog investigations involve a need to scrutinize the actions of more than one outfit.

While the Mounties support national security accountability, inter-agency review "presents the RCMP with some challenges," say briefing notes drafted for Deputy Commissioner Mike Cabana's appearance at a Senate committee last year.

If a review involved an ongoing criminal investigation, the Mounties would be concerned about its potential impact on evidence destined for a court proceeding, say the notes.

"The RCMP would want to prevent operational interference and disclosure of information before the conclusion of an investigation. In addition, review of an active criminal investigation could bring reviewers into the chain of evidence, and might necessitate disclosure at trial or even being called to give testimony."

Justice Dennis O'Connor, who probed the Maher Arar torture affair, recommended changes to allow national security watchdogs to exchange information and conduct joint investigations. He also advocated a co-ordinating committee that would include various security watchdog chairs to ensure seamless handling of complaints and probes.

The watchdog who monitors the Communications Security Establishment has called for legislative changes to encourage and authorize more co-operation between his office and the watchdog that oversees the Canadian Security Intelligence Service.

Talking-point notes prepared for CSE chief Greta Bossenmaier's use last year at a Senate committee say that "changes to our review regime are ultimately a policy question and it would not be appropriate for me to comment."

"I would note, however, that before moving to a 'super-bureaucracy' - with its associated burden and costs - existing review bodies should be optimized and their collaboration should be further facilitated."

The notes prepared in November for Goodale point out that some departments and agencies involved in national security activities lack external review. The most "noticeable omission" is the Canada Border Services Agency, which has a "high number of public complaints that are currently triaged by internal mechanisms," the briefing materials say.

Other federal agencies that have security responsibilities but no external review bodies are Global Affairs Canada, National Defence, the Privy Council Office, Public Safety Canada, and Immigration, Refugees and Citizenship Canada, the notes add.