The union representing tens of thousands of federal scientists says the Conservative government is unfairly silencing its members.

The comments come after Kristi Miller, a researcher for the Department of Fisheries and Oceans, was banned from discussing her work with the media.

Miller's research focuses on the decline of salmon stocks. In January, she was the lead author on an article in the journal Science that suggested the drop in numbers of sockeye salmon in B.C.'s Fraser River might be due to a viral infection.

Reporters lined up to interview her, but the federal government barred her from speaking to the media.

Gary Corbett, president of the Professional Institute of the Public Service of Canada, which represents 57,000 scientists and professionals in the federal and some provincial governments, said it's part of a troubling trend from the Conservatives. Last fall, media reports revealed that the government had imposed strict rules on when and how its researchers can publicly discuss their work.

"Once upon a time, scientists could talk to the press, but it's getting tighter and tighter control," Corbett said. Scientists like Miller are being politicized, he said.

As federal government scientists, their work is funded by taxpayers. But Corbett said when their work doesn't jibe with policy the government wants, they're simply asked to stay quiet, and that's not what they're hired to do.

"What they do is absolutely essential for the public and they protect the public good," he said.

Miller is expected to testify next month at the Cohen Commission, a federal investigation into the decline of Fraser River sockeye salmon.