South African President Thabo Mbeki has called for a reversal of the brain drain

According to the report, Africa lost an estimated 60,000 middle- and high-level managers between 1985 and 1990, and about 23,000 qualified academic professionals emigrate each year in search of better working conditions.

But some professionals suggested that political persecution was often a factor driving the best brains away.

Expatriate replacements for the departing Africans, the report said, are very often more expensive than African professionals.

This situation makes sustainable economic and environmental development even harder.

Britain accused of poaching

Nearly 40 African ministers are attending the conference in Nairobi which is intended to shape Africa's agenda for the summit.

The Natal University report is the latest contribution to the African brain drain debate.

Last year President Thabo Mbeki of South Africa called for a reversal of the situation that regularly see scientists and engineers emigrate to the west.

South Africa's Education Minister Kadar Asmal early this year also accused British recruitment agencies of "raiding" the country of teachers it could afford to loose.

A United Nations conference was also held in Ethiopia last year to consider the issue.

Experts there had called for the improvement in working conditions and more value given to their work.