Bill Gates has called on developed nations to help the world's poorest through greater funding and a more flexible approach to research in the fight against killer diseases.

Speaking to journalists in the Indian city of Chennai, the world's richest man lashed out at attempts by "rich world ... micro ethicists" who demanded that the conditions governing clinical trials on new drugs be carried out in the same way across the world.

He also defiantly argued in favour of research he has funded to find high yielding genetically modified cassava and sorghum to boost nutrition, saying he was ready to fight Europeans and others who opposed such foods.

His comments came towards the end of a week-long visit to Bangladesh and India, where he combined a mixture of high-profile appearances as head of Microsoft with far more discrete inspections of health projects that have benefited from his substantial philanthropy.

Mr Gates and his wife Melinda have earned widespread respect in the health sphere for their work on the search to discover and distribute treatments for "neglected diseases" such as malaria concentrated in the developing world, to which their Foundation has donated more than $6bn in recent years.

Mr Gates was critical of activists he said had stopped clinical trials he helped fund in Cameroun and Cambodia that were designed to see whether the HIV medicine tenofovir could also be used as a prophylactic.

Criticism that developed world standards of care requiring the payment of life-long treatment for any participants who contracted HIV helped terminate the trials.

They were also caught by developed world ethical judgements that the medical support provided to those taking part constituted "inappropriate inducements" in countries where good healthcare is inaccessible to the poor.

Mr Gates stressed the dangers of simply developing new treatments and assuming they would be accessible to developing countries, which often have very por medical infrastructure and suffer a brain drain of their best doctors to richer countries.

Mr Gates praised US initiatives in the fight against AIDS and malaria in developing nations, and said he would boost his efforts to leverage extra funding from the oil-rich states of the Middle East as well as Japan.

He also hinted that he might provide assistance such as the purchase of antiviral drugs for poor countries to redress inequalities in preparations for a potential future outbreak of a lethal form of bird flu.