OTTAWA - The launch of an RCMP investigation into a Tory staffer for political interference in access to information has again exposed the secretive practice of flagging sensitive requests for scrutiny by ministerial aides.

A report this week by Suzanne Legault, Canada's information commissioner, was highly critical of a so-called "purple file" process at Public Works.

An access request in 2009 from The Canadian Press was tagged sensitive, put into a purple-coloured folder, labelled "media," then handed over to Sebastien Togneri, a political aide to then-minister Christian Paradis.

In face-to-face meetings with compliant bureaucrats, and in terse emails, Togneri ordered the release package withheld, then heavily censored, even though he had no legal authority to do so.

Legault recommended the current minister, Rona Ambrose, call in the Mounties to consider whether charges should be laid against Togneri, who quit government last September under fire for other alleged breaches.

Ambrose agreed. Togneri's lawyer, Jean-Francois Lecours, declined comment Tuesday.

The commissioner's report laid part of the blame on a "drift" in the "purple file" process, which was set up under the Tories to alert the ministers to potentially embarrassing requests made under the Access to Information Act.

At Public Works, that alert function had morphed into a political vetting machine. The Canadian Press, citing internal documents, reported last year that Togneri and two other ministerial aides at Public Works had vetted other access requests.

"This purple file process creates a high-risk environment for potential influence or interference," Legault wrote in her 15-page report into a complaint by The Canadian Press.

On her recommendation, Public Works has since ditched the process, forbidden meetings between aides and access officers, and ended any requirement for approval or sign-off at the minister's office.

The purple file process was Public Works' name for a system more commonly known as "amberlighting," which existed under previous Liberal governments -- and was roundly condemned by then opposition leader Stephen Harper, of the Canadian Alliance.

"This entire super-process ... blurs the line between the statutory public service functions of the civil service, and political reporting," Harper told journalist Ann Rees for her 2003 study of the "amberlight" system.

"That to me is really wrong in principle and there is no doubt that this is not in the spirit of the Act."

The Harper Conservatives claimed to have done away with the system soon after taking office in 2006.

Guy Giorno, then Harper's chief of staff, confirmed to a House of Commons committee last April that the prime minister's own department -- the Privy Council Office -- had ended amberlighting.

And as far back as October 2006, a spokesman for then Treasury Board president John Baird said there was no such government-wide policy or procedure.

But amberlighting endured at Public Works, albeit by a less familiar name. Legault reported that the "purple file" system was established after a previous complaint by the Canadian Newspaper Association, which had argued that journalists' requests were excessively vetted and subject to long delays.

The information commissioner largely agreed, and various departments set up systems supposed to eliminate delays while still alerting ministers to potentially embarrassing releases.

Having now demonstrated that Public Works perverted its "purple file" process, Legault is turning her attention to "approval processes" in other departments, spokeswoman Therese Boisclair said Tuesday.

The commissioner is also examining other specific allegations of political interference at Foreign Affairs, National Defence and Public Works, and will deliver a report about the Togneri affair to Parliament on Monday.

A spokesman for Treasury Board, which is responsible for the government's access-to-information policies, said Tuesday that each department sets its own procedures for informing ministers about sensitive requests.

At Treasury Board itself, approval for release is "not required or requested" from the minister's office though political aides are informed of the imminent release of sensitive files, said Pierre-Alain Bujold. That procedure is considered a best practice that was conveyed in a government-wide directive last April, he added.

"Following the release of the information commissioner's special report (to Parliament on Monday), the Treasury Board Secretariat will review the report and assess if further guidance to government departments is required," Bujold said.