The UN Secretary-General delivered tough messages to the Harper Conservatives in Ottawa on Wednesday, urging them to champion climate change and the world's poor at next month's G20 and G8 summits.

Ban Ki-moon wants climate change on the agenda in earnest when Canada hosts the G20 summit in Toronto. He also wants the country to live up to the greenhouse-gas reduction targets it negotiated under the Kyoto Protocol.

"Canada has a special role and special responsibility to play. That is what I am going to emphasize here," Ban said before a scheduled meeting with Prime Minister Stephen Harper.

"I urge Canada to comply fully with the targets set out by the Kyoto Protocol. You can strengthen your mitigation target for the future."

Ban was greeted by a round of applause when he delivered his message to hundreds of academics, diplomats and civil society groups, telling them climate change threatens mankind's survival.

Harper has rejected the Kyoto Protocol, which was negotiated by the previous Liberal government and calls for a six per cent reduction of greenhouse gases by 2020 based on 1990 levels.

The Conservatives have pledged a 17 per cent reduction by 2020, based on 2005 levels, which is in line with U.S. targets but not as tough as Kyoto.

The prime minister is hosting the G20 in Toronto as well as a G8 leaders' summit in Muskoka, Ont., north of the city.

Harper's political opponents tackled the prime minister in the House of Commons, using Ban's comments to push for a greater profile for climate change during next month's talks.

"He's right to say that climate change poses an existential threat to all of us," said NDP Leader Jack Layton.

After his own meeting with Ban, Liberal Leader Michael Ignatieff said Harper should make climate the lead issue at the G20 meeting.

Harper said the G20 will focus on the global economy because that is its function. "I anticipate that a range of subject matters will be talked about, including climate change. This government's position is clear. We support the Copenhagen Accord, which for the first time includes all major emitters."

Ban also called on Harper to press fellow G8 leaders to live up to their previous aid commitments to poor countries and to bring money to the table in Muskoka.

Ban also applauded the Harper Conservatives for making Third World child and maternal health a signature issue at the G8, but he steered clear of any reference to the government's controversial position not to fund abortion-related projects under the initiative.