A study into economic competitiveness in Africa has found that Botswana has the best prospects for economic growth on the continent. The results of the study were released at the annual Africa meeting of the World Economic Forum in South Africa's eastern port city, Durban.

The study found that Botswana was the least corrupt and the best in abiding by contracts and the rule of law on the continent. Also rated highly were Tunisia and Gambia.

Africa's richest country, South Africa, slid into fourth place in this year's study, its rating brought down by perceived costs of organized crime in the country.

The ratings are based on a survey conducted among business leaders who respond to questions about the quality of the environment in which they conduct their enterprises.

Fiona Power, an economist with the World Economic Forum, told South African national radio the business leaders are questioned on their impressions of corruption, adherence to contractual obligations and the rule of law.

"We basically looked at two dimensions, contracts and law and corruption," she explained. "Under contracts and law we look at four variables: the independence of the judiciary, the neutrality of the government when making decision, the costs of organized crime, and financial property and assets are clearly delineated and protected in law.

Under the area of corruption, we look at the pervasiveness of irregular payments in three areas: one is export and import permits, and irregular payments in terms of tax payments, and then irregular payments for connection to public utilities."

Zimbabwe was rated 16th out of 21 African countries surveyed, with its judiciary seen as the least independent. Nigeria and Chad were at the bottom of the list. The public institutions in both countries were rated the worst in Africa.