An organization known for its efforts to improve scientific integrity within the U.S. government is taking aim at Prime Minister Stephen Harper over policies and funding cuts that it says are detrimental to Canadian public science.

In an open letter released Tuesday, the Union of Concerned Scientists urged Mr. Harper to lift a communications protocol that prevents federal researchers from speaking with journalists without approval from Ottawa. The letter also refers to barriers that it says inhibit collaboration with colleagues in the broader scientific community.

The letter is accompanied by more than 800 signatures, largely those of academic researchers working at universities in the United States and other countries outside Canada.

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The letter was released jointly with the Professional Institute of the Public Service of Canada (PIPSC), the union that represents more than 15,000 scientists employed within a range of government departments and agencies. It includes a reference to a PIPSC survey, conducted in 2013, which found that 90 per cent of more than 4,000 of the federal scientists who responded felt they could not speak freely about their work.

Dennis Hansell, chairman of the Department of Ocean Sciences at the University of Miami, is one of the signatories who said he was concerned that Canadian federal researchers faced obstacles in working with academic colleagues both in Canada and abroad.

"As a global scientist I need Canadians to be involved so I can get my work done too. If there's any threat to that, that's a problem," said Dr. Hansell, who is in the midst of proposing a project in the Arctic that would require the co-ordination of U.S., German and Canadian research teams.