OTTAWA - Stephen Harper and fellow G20 leaders will host a special guest at their Cannes summit later this week, one that aid groups are counting on to deliver a message that goes beyond the global financial crisis.

Philanthropist Bill Gates will present some firm ideas on reducing poverty and fostering development in the Third World, and some of it might not sit well with Canada's prime minister.

French President Nicolas Sarkozy, who hosts this week's G20, asked the Microsoft founder to find new sources of innovative financing to tackle food shortages and climate change in the Third World.

Gates is expected to recommend a tax on financial transactions that would help pay for climate-change adaptation strategies in poor countries as well as fighting poverty.

While world leaders will be seized with the sovereign debt crisis, the issue of international development has a featured spot at the G20 because Sarkozy placed food security firmly on the agenda.

"I'll be taking a message to the G20 that we can't turn our backs on the world's poorest, even in these tough economic times," Gates said last week.

The UN Special Rapporteur on the right to food said Monday that the G20 leaders need to take bold action on food security otherwise the world won't be able to feed the estimated nine billion people that will inhabit the planet by 2050.

"Time is running out for world leaders, who must go beyond rhetoric and deliver change. The hungry cannot wait," said Olivier De Schutter.

Gates will table a report that will show "how innovations and partnerships in health and agriculture can help increase global stability and put the poorest countries on a long-term path to economic growth," says a statement from the foundation he and his wife, Melinda, have founded.

Gates said the famine in the Horn of Africa is "unconscionable" and something the world cannot ignore. He is taking the G20 to task for ponying up only half the $22 billion in food security pledges it made in 2009.

Gates's final report to the G20 won't be tabled until Thursday, but a draft summary is in wide circulation.

Mark Fried, senior policy adviser for Oxfam Canada, said it contains a couple of key provisions — new taxes essentially, that won't be warmly received by Harper.

Gates will recommend a tax on financial transactions that would help pay for climate change adaptation strategies in poor countries as well as fighting poverty, said Fried.

Harper has steadfastly opposed such 'Robin Hood'-style international taxation, saying it penalizes Canada's banks for their good behaviour during the recent recession.

Gates is also proposing a levy on shipping-industry fuel to reduce emissions from one of the largest sources of carbon.

"We think it's a terrific proposal, one that has great validity and we hope the prime minister will consider it," said Fried.

Harper's office said Monday it would have more to say after Gates presents his report later this week, but noted that Canada has had great partnerships with his foundation in the past.

"Canada places a high priority on food security. We were one of the first, if not the first, to meet our commitment made on this matter at the G8 in L'Aquila, Italy, in 2009," said spokesman Andrew MacDougall.

"We value the efforts Mr. Gates is making in this and other areas, most notably in child, newborn and maternal health and in eradicating polio."

Harper may not like hearing new tax proposals, but non-government organizations suggest he could find common cause with Gates to get fellow G20 countries to meet their food security pledges.

Groups such as Oxfam, Plan Canada and World Vision laud the Harper government's commitment to food security. They credit the Conservatives with not only living up to financial commitments but also "untying" food aid. That allows the UN World Food Program to shop locally instead of relying exclusively overseas shipments of Canadian food.

"I think that this government has been pretty consistent in terms of carving out a leadership role. If the prime minister speaks at an event like this, nobody's going say, clean up your own backyard," said Rosemary McCarney, the CEO of Plan Canada.

Tiffany Baggetta, spokeswoman for World Vision Canada, said the G20 includes emerging economies such as India, Brazil and South Africa that are also "dealing with poverty in their own backyards."

Baggetta said Canada can show global leadership by pushing other G20 leaders to address the food security crisis.

"With the drought in the Horn of Africa and famine in areas of Somalia, the timing couldn't be more critical to get food security right. Global leaders can do this in France later this week."