Prime Minister Stephen Harper and his government are breaking the law by withdrawing from the Kyoto Protocol, Green Party Leader Elizabeth May said Tuesday.

"Not only has Canada just ended our commitments under an international treaty, I believe we are in violation of domestic law," May told a news conference on Parliament Hill.

"The Kyoto Implementation Act was passed by the House of Commons in 2007 and has royal assent. It requires Canada to continue reporting and doing its job, fulfilling its obligations under the Kyoto Protocol," she said. "I wonder that the prime minister of this country thinks he can withdraw us from an international treaty which was ratified by the House of Commons with no discussion in the House, and violate a domestic law with no discussion in the House."

Environment Minister Peter Kent announced Monday that Canada is withdrawing from Kyoto after he returned from Durban, South Africa, where he attended the UN conference that concluded Sunday with countries agreeing to start negotiations on a new climate change accord.

Kent went to the meeting with a clear position that Canada was not willing to sign on to an extension of the Kyoto deal and it was widely expected that the Conservatives would announce a formal withdrawal from the protocol once the environment minister got home.

"Kyoto for Canada is in the past. As such, we are invoking our legal right to formally withdraw," the environment minister said Monday.

The Kyoto Protocol, which expires next year, committed major industrial economies to reducing their annual CO2 emissions to below 1990 levels, while providing financial supports to developing nations to encourage them to follow suit eventually. Canada ratified the accord in 1997 but was not on track to meet its legally binding targets.

Pressed about the government's decision in the House of Commons Tuesday, Harper said the Kyoto targets were "stupid" and made no sense for Canada.

"In terms of climate change, we're pursuing policies domestically and nationally and internationally. We're working for the creation of an international protocol that will include all major emitters," Harper said.

"What this government has never favoured is ... the protocol that only controls a little bit of global emissions, not enough to actually make any difference but enough to transfer Canadian jobs overseas. And we will never agree to that."

The Conservatives have committed to 17 per cent cuts from 2005 levels by 2020, a much lower threshold to meet than cutting below 1990 emissions levels.

Canada had to notify the United Nations of its intent to withdraw from Kyoto by the end of the year or face additional cuts under the accord based on a five-year audit being conducted at the end of 2012.

Kent said pulling out of Kyoto will save the government an estimated $14 billion in penalties, but May rejected that claim Tuesday.

"That is one of the most bogus things I've ever heard any government minister say. It would have been laughable except that this is tragic. It's completely untrue that we would risk a dime," May said.

Kent's press conference was full of false excuses for withdrawing from the treaty, the British Columbia MP said.

"The hyperbole was palpable, but none of it is true," she said.

May, who said Canada went to Durban in bad faith and obstructed progress on a new deal to reduce greenhouse gas emissions, said the country's international reputation has been severely damaged. Canada won't be seen as a trustworthy partner, said May.

International reaction to Kent's announcement continued Tuesday with countries urging Canada to stick with Kyoto.

Reuters news agency reported that China called the decision "regrettable" and called on Canada to continue abiding by its commitments on climate change.

"It is regrettable and flies in the face of the efforts of the international community for Canada to leave the Kyoto Protocol at a time when the Durban meeting, as everyone knows, made important progress by securing a second phase of commitment to the protocol," Foreign Ministry spokesman Liu Weimin said at a news briefing. Japan also called the action regrettable and made similar encouragements for Canada to stay in Kyoto, Reuters reported.

Environmental groups also reacted to the news.

"The Harper government has imposed a death sentence on many of the world's most vulnerable populations by pulling out of Kyoto," Greenpeace Canada campaigner Mike Hudema said.

The Conservatives are more concerned with expanding Alberta's oilsands developments and reaping the economic benefits than shrinking greenhouse gas emissions and ensuring a healthy future for the next generation, she said. May noted that approval for a new oilsands development was announced last week while negotiations were underway in Durban.

"The message to the rest of the world is pretty clear: Canada doesn't give a damn," she said.

The NDP and Liberals both expressed their disappointment with the government's decision and May said with all of the opposition parties on side, she hopes they can mobilize Canadians to convince the Conservatives to backtrack on the withdrawal.

She said she is not giving up and vowed to keep fighting.

By not being part of Kyoto, Canada would no longer be obliged to file reports on its greenhouse gas emissions and May demanded to know whether Harper will scrap all monitoring programs.

In a statement responding to a report by Commissioner of the Environment Scott Vaughan released Tuesday, Kent said the government is committed to scientific excellence and takes its responsibility to monitor air quality seriously.

Vaughan said at a news conference after tabling his annual report that Kent's announcement is also prompting a reaction from his office and he is looking at the legality of the decision.

He said he has a legal mandate to inform Parliament about the goverment's progress in meeting Kyoto targets.

"So with the announcement of Minister Kent yesterday, we will now have to go back and look at what we do. But what I will say is if the act of Parliament remains the act of Parliament, meaning the Kyoto Protocol Implementation Act, then we will abide by the law. So if the act remains, then we will inform Parliament and the question will be how will we do this," he said.

The next report mandated under Kyoto is supposed to be tabled in the spring. Vaughan said his office has a team that will come up with a plan shortly on how to proceed.