TORONTO - One of the world's leading scientific journals is accusing the Harper government of limiting its scientists from speaking publicly about their research.

The journal, Nature, says in an editorial in this week's issue that it's 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.

It says the U.S. has adopted more open practices since the end of George W. Bush's presidency while Canada has gone in the opposite direction.

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

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, including one last fall when Environment Canada barred Dr. David Tarasick from speaking to journalists about his ozone layer research when it was published in Nature.