"Too often private 'shell' companies with opaque ownership structures are awarded lucrative concessions, with little information available as to who the beneficial owners of the company are," anti-corruption group Global Witness said in a report on its Web site.
Global Witness said both countries have a history of corruption. Angola has opened the books on crude oil revenue as it works out the final details of a $1.4 billion loan from the International Monetary Fund. Nigeria has adopted similar transparency measures, though Global Witness said both countries have to do more to address corruption.
Nigeria produced around 2 million barrels per day and ranks 143rd in an index released by Transparency International. Angola produces around 1.8 million bpd and ranks 168th out of 182 rankings in the transparency index.
"African countries with mineral resources have too long been held back from prosperity by a baleful history of collusion between corrupt and incompetent rulers," Global Witness said. "More transparency would ensure a more open competition and one that is fairer to countries and their citizens."