Environment Minister Jim Prentice says Canada was a "constructive force" in climate change talks taking place in Poland, dismissing criticisms that Canada was obstructing progress at the UN conference.

"We are making progress and we do have a good plan," Prentice told reporters during a conference call Thursday after delivering two speeches at the United Nations climate change conference in Poznan, Poland.

Prentice told the conference Thursday that all major emitters of greenhouse gases must take urgent action on climate change, and said Canada is committed to a "shared vision" for reducing greenhouse gas emissions.

"That shared vision must ensure continued economic growth and sustainable development while reducing global greenhouse gas emissions by at least 50 per cent by 2050," said Prentice.

But Prentice kept firm on the government's previously stated targets, saying Canada was aiming for a 20 per cent reduction of 2006 greenhouse gas levels by 2020. He also said Canada had set a goal of meeting 90 per cent of electricity needs from non-greenhouse-gas-emitting energy sources such as nuclear, hydro, clean coal or wind power by 2020.

Environmental groups have been calling on Prentice to base the government emission reduction targets on 1990 levels, a more ambitious reduction, and the basis for the targets in the Kyoto Protocol.

Prentice's comments come amid criticism from environmental groups that Canada is one of the nations blocking progress at the climate talks, which seek to hammer out the next phase of the Kyoto agreement, to be signed in Denmark next year.

Environmental groups, including the Sierra Club of Canada and David Suzuki Foundation, issued a statement saying that while Prentice's speeches "seemed to signal a change in tone," they were "disappointing" in their lack of firm commitments.

"Over the past week, Canada has taken a shameful role here," the environmental groups said in a joint statement. "Our country has been singled out as a spoiler. And the minister's speeches today did not contain any signal that Canada will do the right thing and commit to the science-based emission targets and scaled-up financing that the world needs to avert dangerous climate change."

Canada also was criticized for being one of four nations, along with the United States, Australia and New Zealand, opposed to the inclusion of language recognizing the "rights" of indigenous peoples in a proposal aimed at reducing deforestation. The text of the draft of the Reducing Emissions from Deforestation and Degradation (REDD) proposal instead refers to the "full and effective participation" of indigenous people.

Prentice responded, saying aboriginal people and indigenous people would be consulted as part of any discussion related to forests in their traditional territory. But he said the inclusion of references to a UN Declaration on the Rights of Indigenous Peoples was out of place in the REDD proposal and had "nothing to do with climate change."

The Poznan conference ends on Friday.