Prime Minister Justin Trudeau has rebuffed fresh demands for a public inquiry into the unauthorized RCMP surveillance of two journalists.

"It's wholly unacceptable that this happened in Canada," Trudeau said in the House of Commons on Wednesday. "It was a mistake, it's been settled and we've learned from the situation."

The prime minister was responding to renewed pressure from NDP Leader Tom Mulcair for a formal inquiry into the August 2007 incident, in which undercover officers quietly tailed two reporters from La Presse over nine days.

NDP Leader Tom Mulcair is demanding a public inquiry into the RCMP spy operation against two La Presse journalists, saying the episode can't be dismissed as a mere mistake. (Adrian Wyld/Canadian Press)

In an exclusive report, CBC News last week cited an internal document showing the officers failed to get the permission of Bob Paulson, then acting assistant commissioner and now commissioner of the RCMP, to carry out the surveillance. Once they did ask for a green light, it was refused.

The document, with some parts censored, was obtained under the Access to Information Act.

The RCMP officers were trying to find out who leaked to La Presse a sensitive government document referring to suspected terrorist Adil Charkaoui, alleging he had discussed blowing up a plane in 2000.

References to a possible RCMP surveillance operation emerged last fall from court documents in a separate case, but the CBC News report last week produced evidence confirming the unauthorized surveillance in fact took place.

This affects one of the foundations of our democracy, freedom of the press. - NDP Leader Tom Mulcair

"This affects one of the foundations of our democracy, freedom of the press," Mulcair said in the House of Commons on Wednesday, repeating his demand for a public inquiry.

Last week, La Presse's vice-president and deputy editor, Eric Trottier, wrote to Paulson also asking for a public inquiry to assure there will never be a repeat of the incident. The May 25 letter was also sent to Trudeau and Public Safety Minister Ralph Goodale, who is responsible for the RCMP.

RCMP Commissioner Bob Paulson met with a La Presse journalist on Dec. 3 last year but neglected to mention an important element of the spy operation, says a May 25 letter from the paper's deputy editor. (Sean Kilpatrick/Canadian Press)

Trottier's letter, obtained by CBC News, also noted Paulson had met with Joel-Denis Bellavance, one of the Ottawa journalists who was watched, on Dec. 3 last year in Ottawa to explain that the 2007 operation was never authorized.

But the missive said Paulson failed to mention at the meeting that in 2008 he did authorize surveillance of Bellavance for a limited period, though officers never carried it out.

Bellavance has said he was never aware of the 2007 surveillance, though had cut off contact with his source as a precaution. He said the RCMP has never contacted the source, who remains anonymous.

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