Natural Resources Minister Gary Lunn said Wednesday he fired the president of Canada's nuclear watchdog because she showed a "lack of leadership," but critics slammed the government for interfering in an independent agency.

Lunn told a Commons committee that Linda Keen, head of the Canadian Nuclear Safety Commission, did not act quickly enough following the shutdown of the Chalk River nuclear reactor in Ontario late last year.

Keen was fired late Tuesday night, 12 hours before she was scheduled to speak before the committee.

Liberal MP David McGuinty accused the Conservatives of using U.S.-style partisan attacks to intimidate independent agencies.

"Anybody who tries to do their job around this town these days seems to lose it," he told Lunn. "These are the kinds of Republican tactics this town has never seen before."

Bernard Shapiro, the former head of McGill University, resigned as the federal ethics commissioner last year after run-ins with Prime Minister Stephen Harper's government. And Chief Electoral Officer Marc Mayrand was publicly criticized by Harper for allowing veiled women to vote without showing their faces.

The natural resources committee has been set up to probe the circumstances surrounding the Chalk River closure -- which led to a worldwide medical isotope shortage.

The reactor, operated by the Atomic Energy of Canada Ltd. (AECL), a Crown corporation, stopped production for scheduled repairs on Nov. 18 and was expected to restart within five days.

But the CNSC -- responsible for setting licensing, health and safety rules for the country's nuclear facilities -- refused to allow the reactor to restart after finding it had been operating without a backup emergency power system for cooling pumps for 17 months.

"The obvious culprit here is the Crown corporation," Green Party Leader Elizabeth May told CTV Newsnet.

She said the AECL was operating in violation of its licence and had failed to anticipate that a shutdown would imperil the supply of medical isotopes, while Keen was simply doing her job.

"Keen was fired because they're making her a scapegoat; she was fired because she did not knuckle-under to a minister," said May.

New Democrat MP Paul Dewar, the party's deputy critic for Crown corporations, said Lunn should not have put pressure on Keen because of her position as a quasi-judicial official.

"The wrong person got fired yesterday, in my opinion," Dewar told CTV's Mike Duffy Live. "The person who should have been fired was Mr. Lunn, who crossed over a line. These are boundaries that are sacrosanct in terms of good governance. For public servants to do their job, they have to do it without this kind of interference."

In December, emergency legislation passed by Parliament side-stepped the CNSC's objections and allowed AECL to restart the reactor for 120 days in order to alleviate the isotope shortage.

Since then, Keen and Lunn have been engaged in a very public dispute over the shutdown of the nuclear reactor.

"The president of the CNSC is a chief executive officer and is responsible for supervision over the direction of the work of the members, officers and employees of the commission," Lunn told the committee on Wednesday.

"At issue was the president's failure to manage the work in order to bring the matter for hearing before the commission in an appropriately urgent fashion."

Lunn said Keen failed to "consider fully, in a timely fashion, the serious consequences of the growing shortage of medical isotopes."

He said her actions were troubling and that she didn't meet the high standards of the government or the Canadian people.

Keen fired

Opposition leaders have called on Lunn to resign, accusing him of improperly interfering with an arm's-length nuclear regulator.

Following Lunn's statement Wednesday, Liberal MP Omar Alghabra accused the minister of "blatant political interference.''

"I think the prime minister fired the wrong person today,'' he said.

Bloc Quebecois MP Claude DeBellefeuille said Lunn's behaviour "undermined the credibility of the commission.''

The Tories informed Keen that she was fired in a letter sent late Tuesday.

A press released posted on the CNSC website said Keen "received a letter from the Privy Council Office indicating that the government adopted an Order in Council terminating her designation as President of the Commission, effective immediately."

The letter further indicates that she remains a full-time permanent member of the Commission.

In a letter dated Dec. 27, which was later leaked to the media and then posted on the CNSC website, Lunn threatened to fire Keen for her role.

Keen responded with a scathing letter, telling Lunn that "the allegations which have been made, coupled with your threat to have me removed as President, seriously undermine the independence of the CNSC."

With a report from CTV Ottawa Bureau Chief Robert Fife and files from The Canadian Press