'In the last few years we've seen -- under the Harper government, at least -- a real concerted effort to keep controls on what the evidence is saying,' says Kathryn O'Hara, president of the Canadian Science Writers' Association. (Canadian Science Writers' Association)

The party leaders vying to form the next Canadian government are being urged to "take off the muzzles" from federal scientists.

A group representing 500 science journalists and communicators across Canada sent an open letter Tuesday to Conservative Leader Stephen Harper, Liberal Leader Michael Ignatieff, NDP Leader Jack Layton and Green Party Leader Elizabeth May documenting recent instances where they say federal scientists have been barred from talking about research funded by taxpayers.

"We urge you to free the scientists to speak," the letter said. "Take off the muzzles and eliminate the script writers and allow scientists — they do have PhDs after all — to speak for themselves."

Kathryn O'Hara, president of the association, said openness and transparency are issues that haven't come up much in the election campaign, and her group felt it was important to ask about them.

The federal government spends billions each year on scientific research, and taxpayers must be able to examine the results, she said, otherwise, "how can you get a real sense of … value in money going toward science?"

The public also needs to be able to see whether government policy is based on evidence uncovered using taxpayer money, she added.

"In the last few years we've seen — under the Harper government, at least — a real concerted effort to keep controls on what the evidence is saying," O'Hara said.

The letter included examples of cases where federal scientists were the lead authors of high-profile papers on salmon and climate change, but were not permitted to give interviews.

O'Hara added that when scientists can't answer questions, it is difficult for journalists to do a good job covering their research, and the public could end up misinformed.

The letter noted that all political parties "repeatedly make promises to promote government openness and accountability" and asked the party leaders to explain how they would guarantee freer channels of communication.

O'Hara said she hopes the federal leaders will acknowledge that there is a problem and that it is important to disseminate government science to the public.

The association held talks last year with senior bureaucrats in an effort to gain "timely access" to federal scientists who had published articles in journals or presented papers at conferences, O'Hara added, but afterward, "nothing changed substantially."

Liberal science critic Marc Garneau says his party believes 'that a healthy civil service should allows its scientists to speak as long as they don't get into policy.' (Canadian Press)As of Tuesday afternoon, O'Hara had not heard back from any of the party leaders about the letter.

However, Marc Garneau, Liberal candidate for Westmount-Ville-Marie and the Liberal critic for industry, told CBC News Tuesday that things would change under a Liberal government for the majority of topics that don't pose privacy or security risks.

"We would remove the gag order that's been put on our scientists," he said. "We believe that a healthy civil service should allows its scientists to speak as long as they don't get into policy."

As of late Tuesday afternoon, representatives of the Conservatives and the NDP had not responded to a request for comment.