For years, the Conservative government has been accused of "muzzling" federal scientists by controlling who they're allowed to talk to and what they can say about their own research.

Just this week, recently retired Fisheries and Oceans Canada biologist Steve Campana went public with his own experiences of strict directives, cumbersome approval procedures and arbitrary media rejections while working with the agency.

It's just one of numerous complaints from both scientists and the media about federal scientists being restricted from publicly talking about their research.

So what is at stake? Here are a few frequently asked questions.

How are scientists being muzzled?

In 2006, the Harper government introduced strict procedures around how its scientists are allowed to speak about their research to the media.

In the past, journalists were generally able to contact scientists directly for interviews, but after these new directives they had to go through government communications officers.

And scientists had to get pre-approval from their minister's office before speaking to members of national or international media, a process that can involve drafting potential questions and answers, which are then scrutinized by a team before the green light is given.

Didymo or "rock snot" has been found to be non-invasive algae. This discovery debunks the assumption that didymo was introduced to rivers by humans and suggests that didymo blooms may be linked to global climate change. (Michel Chouinard/Queen's University) In one instance from 2014, a request from The Canadian Press to speak to federal government scientist Max Bothwell about his work on algae led to a 110-page email exchange to and from 16 different federal government communications officers.

In the end, Bothwell was not interviewed before the Canadian Press article was published.

A 2014 study of media policies from 16 federal departments concluded that current policies place far more restrictions on Canadian scientists when it comes to talking to media than is the case with their U.S. counterparts.

There have also been reports of restrictions on scientists being able to travel to conferences to share their results. Some international scientists have also voiced concerns that working with Canadian scientists will affect their own ability to speak freely about research results.

In other cases, scientists have described a "broader chill" within the scientific community, where they aren't directly prevented from speaking out, but feel pressure to stay quiet.

What are some examples of interference?

In 2010, Natural Resources Canada scientist Scott Dallimore was not allowed to talk about research into a flood in northern Canada 13,000 years ago without getting pre-approval from political staff in the office of then-Natural Resources minister Christian Paradis. Postmedia News said requests were only approved after reporters' deadlines had already passed.

In 2011, Department of Fisheries and Oceans scientist Kristina Miller was blocked from speaking to the media about her research suggesting viral infections may be linked to higher salmon mortality.

Environment Canada's media office granted no interviews after a team published a paper in 2011 concluding that a 2 degree C increase in global temperatures may be unavoidable by 2100.

Postmedia science reporter Margaret Munro requested data from radiation monitors run by Health Canada following the earthquake and nuclear plant problems in Japan. Munro said Health Canada would not approve an interview with one of its experts responsible for the detectors.

How has the scientific community responded?

In recent years, scientists as well as members of the media have become increasingly vocal against what has been called the Canadian government's "War on Science."

Hundreds of scientists staged a mock funeral procession in Ottawa to protest Conservative government policies they claim are causing the 'death of evidence.'

Science journalist Kathryn O'Hara first sounded the alarm in 2010 in a column for the science journal Nature. She wrote that climate change researchers from Environment Canada were "prevented from sharing their work at conferences, giving interviews to journalists, and even talking about research that had already been published."

In her letter, she urged the government to loosen its strict controls.

Scientists and concerned citizens have since staged protests across the country, including a mock funeral on Parliament Hill in 2013 to mourn what they called the death of scientific evidence.

There have also been open letters written by science organizations, journalists and groups of international scientists calling for the unmuzzling of scientists. A letter signed by more than 800 scientists from 32 countries asked Prime Minister Stephen Harper to end "burdensome restrictions on scientific communication and collaboration faced by Canadian government scientists."

A complaint lodged by advocacy group Democracy Watch and the University of Victoria's Environmental Law Clinic in 2013 led to the launch of an investigation by Canada's information commissioner Suzanne Legault, which is still ongoing.

Despite the outcry, the strict controls still seem to be firmly in place. A survey conducted last year of 4,000 Canadian scientists found that 74 per cent thought the sharing of government science findings with the Canadian public had become too restricted.

How has the government responded to the claims?

The Harper government has repeatedly denied claims of political interference in public science. In fact, several ministers have insisted that since coming to power in 2006, the government has provided record investments in science and technology.

"Canada is ranked number one in the G7 for our support for research and development in our colleges, universities and other institutes," Greg Rickford, then-minister of state for science and technology, said in a statement to the Fifth Estate last year. "Research is vibrant and flourishing right across the country."

His successor, Ed Holder, has repeated similar statements through his spokesman, Scott French. "While ministers are the primary spokespersons for government departments, scientists have, and are readily available to share their research with Canadians," French said in October 2014.

He added that federal departments and agencies produce over 4,000 science publications per year, including 700 peer-reviewed articles last year alone.

What impact does this have on Canadians?

Critics of the restrictions say that the policies undermine government transparency and accountability and that without open communication, Canadians have little knowledge of the research that is being funded by their own tax dollars, or how this research might be utilized in other contexts.

Gary Corbett, President of the Professional Institute of the Public Service of Canada (PIPSC) holds a press conference at the National Press Theatre in Ottawa, Monday Oct. 21, 2013, to reveal the results of a major survey hosted by Environics Research to gauge the scale and impact of "muzzling" and political interference among federal scientists. (Sean Kilpatrick/Canadian Press)

"Forget excitement, it's hard to even maintain public trust in taxpayer-funded research when scientists are not allowed to explain their work," O'Hara wrote in her Nature column. "Government media officers also find it difficult to craft informative press releases and bring research to media attention."

Some observers have also pointed out that freedom of knowledge is necessary for good policy making.

"The Canadian standard of living is, in large measure, a result of scientific discovery and technological innovation," Scott Findlay, a co-founder of Evidence of Democracy and a professor of biology at the University of Ottawa, said in 2013.

"So every Canadian has a vested interest in the health of public science, and the use of scientific evidence to protect and sustain the values we hold."