The Friends of the Earth presented Environment Minister Rona Ambrose with a legal opinion asserting that Canada is in breach of the international treaty to reduce air pollution that causes global warming, and asked her to respond.

Otherwise, "I anticipate we would be on our way to federal court within six months," said Friends of the Earth chief executive Beatrice Olivastri.

"Canada has a moral responsibility and a legal duty to act to reduce greenhouse-gas emissions," she added.

A lawsuit would invoke the Canadian Environmental Protection Act to force the minister to uphold Canada's pledge under the Kyoto Protocol to reduce greenhouse-gas emissions to six percent below 1990 levels by 2012, she said.

Emissions instead have increased by 26.6 percent.

Ambrose proposed a plan in mid-October to reduce carbon-dioxide emissions that cause global warming by up to 65 percent by 2050, based on 2003 levels.

The draft law would also apply intensity-based targets until 2020, allowing emissions to continue to rise until then, prompting environmentalists to accuse Ambrose of stalling.

Opposition members of Parliament promised to defeat the bill. New Democratic Party leader Jack Layton went further, saying he would not rule out trying to topple Canada's minority Conservative government over the issue.

Layton also proposed alternative legislation Tuesday to force cuts in greenhouse-gas emissions of 25 percent below 1990 levels by 2020, climbing to an 80 percent cut by 2050.

"With this bill ... Canadians will no longer have to hold their breath waiting for the politicians to take action," he said.

The threat of a lawsuit comes one day after officials said Canada would seek a "comprehensive review" of the 1997 Kyoto Protocol when representatives of 165 countries meet next week in Nairobi, Kenya to discuss its next phase.

A senior official said Canada hopes to focus on "the longer term."

Ambrose has said large polluters such as India and China must accept emissions reduction targets in the next phase of the accord.

She also said Canada would not buy carbon emission rights on an international market after failing to meet its target to curb pollution under the pact.

The innovative market was introduced to control carbon gases emitted mainly by burning oil, gas and coal.

Its backbone is the European Union's Emissions Trading System, which forces 11,500 firms that are big users of fossil fuels to meet a carbon-dioxide emissions target or pay a penalty.

Those that are below their quota can sell their surplus to companies that exceed it.

In May, the fledgling market ran into trouble when prices tumbled as European countries discovered they were polluting far less than they thought.

The Friends of the Earth said its legal opinion would also be submitted to the Kyoto Protocol Compliance Committee to add weight to a complaint already lodged by South Africa over Canada's failure to report "demonstrable progress to reduce greenhouse gas emissions" in 2005.

South Africa asked the committee in May to investigate the failure of 15 countries, including Canada, to report on their progress, as required.

If Canada is found to be non-compliant, it faces an additional 30 percent reduction penalty and its ability to trade emissions credits would be suspended, further hampering its options to meet its Kyoto target.

The conclusion by German legal expert Roda Verheyen that Canada is "in breach of international law" is based on a recent Canadian environment auditor's report, she said.

The September report found that Canada must realize "a massive scale-up of efforts" to fight global warming after lagging far behind other countries.

John Bennett of the Climate Action Network said he hoped the threat of legal action would "make Canadians aware that on their behalf, international agreements are being violated," and prompt a political backlash.

"This is the first time in Canadian history that the government of Canada is actually repudiating its responsibility under an international agreement and actively trying to undermine it," he said.

"This is not something the Canadian people will accept."

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