Auditor-General Sheila Fraser will face a grilling from parliamentarians on Wednesday over why she fired Environment Commissioner Johanne Gelinas.

The House of Commons environment committee wants answers, and Gelinas herself pronounced shock.

"I was considering a future departure, but today's announcement from Sheila Fraser was premature and came as a complete surprise to me," Gelinas, who is out of the country, wrote in the statement on Tuesday night.

Fraser issued a news release on Tuesday saying Gelinas had left the position to "pursue other opportunities.

"Madame Gelinas and her team have done valuable work assisting parliamentarians through their audits of government's management of its environmental and sustainable development responsibilities."

Reports say that Gelinas, who held the position for five years, was fired for being too much of an advocate on policy.

Gelinas admitted a "difference of opinion" with Fraser, but did say the government had nothing to do with her termination.

"The discusssions (Fraser and I) had were in private, with no interference whatsoever from the Government of Canada and its representatives," she wrote.

The Canadian Press reported that Ron Thompson, an assistant auditor-general, had essentially replaced Gelinas months ago. Fraser has officially named him as Gelinas' interim replacement.

Gelinas worked as part of the Office of the Auditor-General, an independent office, and examined the government's effectiveness in its environmental programs.

Gelinas' report last September caused a major stir as it slammed the previous government's record on the environment and outlined measures the new government should take to address climate change.

Fraser appeared before the House of Commons environment committee on Tuesday.

She informed MPs on the environment committee that she would like a review of the role of the environment commissioner, particularly the extent to which he or she should be involved in "advocacy" regarding government policy.

That would be complete by autumn, at which point a permanent replacement would be named, she said.

CTV's David Akin said that when the position was created, it was originally conceived to be an independent position that would report directly to Parliament. For various reasons, that didn't happen.

Canada is one of only two countries with an environment commissioner, and this firing will create more debate about the role, he said.

Political reaction

Environment Minister John Baird spoke in defence of Gelinas' record.

"Commissioner Gelinas had done a phenomenal job. She was great at exposing some of the real shortcomings and environmental policies in recent years," he said.

"When I heard she wanted to leave government, one of my first thoughts was, 'How do I nominate this woman for The Order of Canada?'"

Liberal Leader and former environment minister Stephane Dion told reporters: "I cannot believe she has been fired. She has been a very good commissioner, a tremendous one. She was demanding for the ministers -- and it was her job -- and I learned working with her."

"Well, it's a sad day for Canada and the environment that Madame Gelinas is no longer in this key position, where she was a respected, non-partisan voice holding our government to account," NDP Leader Jack Layton told reporters.

Green Party Leader Elizabeth May asked Fraser to reconsider.

"Auditor General Sheila Fraser is, without doubt, one of the most respected women in Canada," said May.

"My respect for her is not diminished, but I appeal to her to reconsider. This decision smacks of shooting the messenger.

"The independence of the commissioner of the environment and sustainable development is established in the legislation. Neither the government nor Ms. Fraser should attempt to curtail that independence."

With files from CTV's David Akin and The Canadian Press