Transport-for-development charity Riders for Health warned that poor transport links and inadequate health services in remote communities threaten the success of the plans to roll out HIV/Aids drugs in poor countries.
British scientists in Africa are planning large-scale human trials of two anti-HIV gels, designed to combat the Aids virus, in South Africa, Zambia, Tanzania, Uganda and Cameroon. UK international development secretary Hilary Benn has claimed they could save millions of lives once they become available at the end of the decade.
Also this week, the United Nation's Global Fund, Unicef, the World Bank and the Clinton Foundation announced a deal to distribute cheap, generic anti-HIV/Aids drugs in poor countries. Countries will be invited to buy generic drugs produced in India and South Africa at a cost of $140 (£75) a year per patient - less than half the cost of current treatments.
The project will also supply cheaper Aids testing equipment.
Chief executive Barry Coleman said: "Riders for Health are right behind the gel initiative. But we know it will run into precisely the same brick wall as every other initiative of its kind in Africa. There is no reliable transport to get it to the rural communities on a regular basis."
He added that the NGO had worked in Nigeria, Zimbabwe and Gambia for 15 years and knew the problem well. "There is almost no country in Africa that has the transport infrastructure necessary to deliver an aspirin, still less a new Aids prophylactic," said Coleman.
The UN and the Clinton Foundation have noted the low take-up of anti-Aids drugs and condoms in Africa, but, according to Coleman, they mistakenly believe the problem is one of cost or the sexual behaviour of African men.
"Where transport is identified, people think it is because the roads are bumpy and riddled with potholes, but the problem is that while (UN agencies and NGOs) have sent huge numbers of vehicles to Africa, they are not supported by the maintenance systems that we have in the West."
Coleman advised development NGOs to send people to the Riders' academy in the Zimbabwe capital Harare to learn how to drive in Africa and maintain a fleet of vehicles.
"They should then decide if they want to replicate the academies in every country, because we can't do it everywhere," he said. "Otherwise, in a few years Hilary Benn is going to be very disappointed - and he won't understand why."