Canada's environment commissioner Johanne Gélinassaysit came as a "complete surprise" to learn shewas fired, but denied that political interference played a part in her dismissal.

In a statement released late Tuesday, Gélinas said she and her boss, Auditor General Sheila Fraser, had a difference of opinion for almost a year on her role.

"I was considering a future departure, but today's announcement from Mrs. Fraser was premature and came as a complete surprise to me," she said.

Herdiscussions with Fraser, she added, "were in private, with no interference whatsoever" from the government.

In a statement Tuesday, Fraser saidGélinaswas "leaving the position to pursue other opportunities." Fraser also announced a review of environmental and sustainable development audit practices.

But in a confidential memorandumobtained by CBC News Tuesday, Fraser said "sustainable development issues do not appear to have the same impact as our other performance audit work," basing that in part to "how many of our recommendations are implemented."

News ofthe firing came as the environmentissue topped the politicalagendaTuesdayin the House of Commons.

Targeted Liberals,Tories on climate change

In September 2006, Gélinas released a highly critical report attacking the previous Liberal government's effortsto addressclimate change in the past 10 years, while outlining policies for the Conservative government to implement.

She also openly criticized the Tories' recent clean air plan, saying it did little to address the problem of climate change and greenhouse gases in the short term.

Liberal environment critic David McGuinty said Fraser made it clear to the environment committee at a private meeting Tuesday that she felt Gélinas had been taking too much of an advocacy role.

"She is an extremely capable woman who has served the country well. It bothers me enormously," McGuinty said.

Fraser appointed assistant auditor general Ron Thompson as Gélinas's replacement, effective Tuesday.

Fraser'sreview is expected to be completed this fall, the statement said.

Gélinas 'held the government to account': NDP critic

Nathan Cullen, the NDP's environment critic,praised Gélinas for her tireless work inpromoting the environment as a major issue.

"Madame Gélinas has provided the environment community and Canadians with some of the finest work we've seen," Cullen said. "She has held the government to account."

He also warned that there would be repercussions if any political interference contributed to her dismissal.

"If there is any, we will be raising the alarms," he said.

A spokesman for Environment Minister John Baird said the authority to replace the environment commissioner rests entirely with the auditor general.

But Charles Caccia, a former Liberal environment minister who sits on the environment commissioner's advisory committee, said the government must have known about and at least tacitly approved the firing.

"I cannot see how she [Fraser] would go ahead without protecting her back and without letting the government know … or without picking up some signals of criticism of the commissioner from the government and using them as an excuse to proceed with a dismissal."

The Commons environment committee has called Fraser to testify at an open meeting Wednesday to explain Gélinas's departure.

With files from the Canadian Press