The power of the world's richest nations needs to be reined in, Brazil's President Luiz Inacio Lula da Silva has told the World Social Forum (WSF).
President Lula has called for greater help for the world's poorest nations
Speaking in Porto Alegre, Brazil, President Lula urged poorer nations to unite to further their interests.
"We need to build another force so we can change the world's economic and social geography," he said.
The forum is a meeting of activists who campaign for a fair deal for poor countries in global trade.
Meet and greet
It provides an alternative to the World Economic Forum (WEF) taking place this week in Davos, Switzerland. The WEF is a meeting of world political and business leaders, and is famed as a high level networking session.
President Lula, who was preparing to leave for Davos, said that he would tell global leaders there "what I'm telling you here".
The WSF is less impressed by big business and political heavyweights.
Many activists are running out of patience with the world leaders
Even President Lula, a former trade union leader and in Porto Alegre to launch a Global Call to Action Against Poverty, was heckled by a small section of the10,000 crowd, the Associated Press news agency reported.
He was booed and one man threw egg, while outside other activists chanted "Lula come back to reality!"
They also burnt an effigy of Lula and the US stars-and-stripes banner.
President Lula has been accused by some critics of failing to deliver on election promises to reform the economy and improve the lot of Brazil's poorest inhabitants.
Non-governmental organisations at the World Social Forum on Thursday called for greater efforts to cut world poverty.
In Davos on Thursday, UK Prime Minister Tony Blair echoed their comments, calling Africa's poverty "a scar on the conscience of the world".
Other topics on the agenda in Brazil include the rights of indigenous people from across South and Latin America, AFP news agency reported.
About 400 representatives of peoples from the areas including the Amazon, the Andes and Central America are taking part in the meeting at Porto Alegre, AFP said.
They have accused governments of caving in to corporations looking to develop and extract natural resources.