TORONTO - One of the world's leading scientific journals has criticized the federal government for policies that limit its scientists from speaking publicly about their research.

The journal, Nature, says in an editorial in this week's issue that it is time for the Canadian government to set its scientists free.

It notes that Canada and the United States have undergone role reversals in the past six years, with the U.S. adopting more open practices since the end of George W. Bush's presidency while Canada has been going in the opposite direction.

The editorial says that since taking power in 2006, Prime Minister Stephen Harper's government has tightened the media protocols applied to federal government scientists and employees.

Nature says policy directives on government communications that have been released through access to information requests have revealed the Harper government has little understanding of the importance of the free flow of scientific knowledge.

The journal says its own news reporters have experienced firsthand the obstacles the Canadian government puts in the way of people trying to gain access to science generated by government scientists on the public payroll.

"The Harper government's poor record on openness has been raised by this publication before ... and Nature's news reporters, who have an obvious interest in access to scientific information and expert opinion, have experienced directly the cumbersome approval process that stalls or prevents meaningful contact with Canada's publicly funded scientists," the editorial says.

The editorial was referring to a column outlining the problems federal scientists face that it published in September 2010. The column was written by Kathryn O'Hara, a professor of science broadcast journalism at Carleton University in Ottawa and a former president of the Canadian Science Writers' Association.

"Little has changed in the past two years." the editorial continued. "Rather than address the matter, the Canadian government seems inclined to stick with its restrictive course and ride out all objections."

Two weeks ago the Canadian Science Writers' Association, the World Federation of Science Journalists and several other groups sent an open letter to Harper, calling on him to unmuzzle federal scientists.

The letter cited a couple of high-profile examples of the federal policy in action. Last fall Environment Canada barred Dr. David Tarasick from speaking to journalists about his ozone layer research when it was published in Nature. And the Privy Council Office stopped Kristina Miller, a researcher at Fisheries and Oceans Canada, from doing interviews about a study she published in Science on the causes of sockeye salmon decline in British Columbia.

Nature said the Canadian policy surprised international attendees of the recent conference in Vancouver of the American Association for the Advancement of Science. The problem was the subject of a session at the meeting.

"Scientists and other visitors from around the globe discovered, to their surprise, that Canada's generally positive foreign reputation as a progressive, scientific nation masks some startlingly poor behaviour," Nature says.

"The way forward is clear: it is time for the Canadian government to set its scientists free."

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