A Shell subsidiary that makes biodiesel in Brazil has dropped controversial plans to buy sugar cane grown on land taken from indigenous people, Survival International said Wednesday.

The company, Raizen, was set up in 2010 by Shell and Brazil's biofuels giant Cosan to make biofuel from sugar cane -- an endeavor that had been criticized by indigenous groups who say their ancestral lands have been tainted.

Raizen has now signed an agreement with the National Indian Foundation (FUNAI) promising to stop buying sugar cane grown on Guarani territory in the southern state of Mato Grosso do Sul, according to Survival, an NGO that works to defend tribal peoples.

Many Guarani people had been driven off their land, left to camp along roadsides. They also complained that rivers on their traditional lands were being polluted with pesticides.

"Other companies must follow Raizen's example, and stop bankrolling the theft of Guarani land. It's time the world woke up to the fact that Brazil's biofuel is tainted with Indian blood," said Survival director Stephen Corry.

The announcement came as officials opened the UN Conference on Sustainable Development here Wednesday, launching a new round of debate on the future of the planet, its resources and people, 20 years after the first Earth Summit.

Kicking off the so-called Rio+20 summit, Dilma Rousseff, president of host nation Brazil, called on "all countries of the world to commit" to reaching an accord that addresses the most pressing environmental and social woes.