OTTAWA - NDP Leader Tom Mulcair says a public inquiry should be called after it was revealed Mounties monitored two journalists in 2007.

The inquiry would also have to look into whether the higher-ups approved the surveillance, he said.

"I've rarely in my life seen officers acting on their own in something like this. This is an attempt to stifle the ability of journalists to do their crucial work in our democracy," Mulcair said.

Mulcair's comments come after CBC News reported a rogue group of RCMP officers investigating a leak of a secret document spied on the two for more than a week without authorization.

The report, based on a government briefing note obtained by the broadcaster, says Mounties placed two Ottawa-based journalists, Joel-Denis Bellavance and Gilles Toupin, under physical surveillance for nine days in 2007.

CBC also says the surveillance was carried out without the required permission of Bob Paulson, an acting assistant commissioner at the time.

Paulson is now the commissioner of the RCMP.

Prime Minister Justin Trudeau says this is unacceptable and notes an apology has been given to the journalists involved.

Public Safety Minister Ralph Goodale told MPs in question period that freedom of the press is a fundamental Canadian value enshrined in the Charter.

"The unauthorized surveillance was entirely unacceptable," Goodale said. "It was contrary to a ministerial directive, it was contrary to RCMP policy and it was stopped when RCMP headquarters became aware of it, and the investigators have been reprimanded."

With files from CTVNews.ca