But Joel Cohen of the International Food Policy Research Institute (IFPRI) said governments should speed up the granting of permits for trials provided these were done in confined conditions to prevent contamination of plants and animals.

"If more of these small-scale experimental trials were approved, scientists, farmers and decision makers would know very much faster whether or not they should move towards commercial use," he told a news conference.

"If the research stays in the lab, then it will be of no benefit to the farmer," said Cohen, IFPRI's program director for biosafety systems.

IFPRI is a Washington-based body funded by governments, voluntary and humanitarian organisations, UN agencies, scientific institutes and the World Bank.

Anti-GMO activists say so-called Frankenstein foods risk destabilising the environment and food production, for example by creating super-weeds, or might damage those who eat them via unknown side-effects.

GMO producers -- including several in South Africa, which has pioneered GMO research in Africa -- counter that more productive crop strains better able to cope with climatic extremes will help ensure fewer people go hungry in the poorest continent.

Most of Africa's farmers are small scale and their crops are threatened by drought, famine and pests, which could be cushioned by adapting the use of GM crops, Cohen said.

About 65 percent of Africans rely on agriculture, with small-scale farmers accounting for 90 percent of the continent's production, IFPRI says. Allowing pest-proof GM crops would reduce the amount of pesticides used in cultivation and lower the risk of harm to farmers, Cohen said.

"This means in the case of cotton, for example, reducing the number of spraying events from eight or ten times a year, to just three times. It means therefore reducing the risk of adolescent and adult mortality due to exposure or ill use of pesticides," Cohen said.