Angola on Wednesday angrily rejected a report by a human rights group that said $4 billion in oil revenues had vanished from state coffers between 1997 and 2002, calling it an attempt to tarnish its image.
Human Rights Watch said on Tuesday the Angolan government consistently mismanaged revenues in an amount equal to the sum it spent on all social programmes in the five-year period rather than use it for alleviating hunger and disease.
But the Angolan presidency said in a statement no independent audit had ever been carried out to prove Human Rights Watch's accusations.
"The government can't be held responsible for estimated income that is based on non-credible sources, bearing in mind that none of the international financial institutions have to date proven those accusations," it said.
It called the report "yet another crusade against the good name of Angola and its leaders".
The corruption charges were similar to ones made by the International Monetary Fund and others over the past year.
Some 27 years of war in Angola ended in 2002 but some 900,000 Angolans remain homeless. Millions more have virtually no access to hospitals or schools and United Nations agencies estimate that about half of the country's 7.4 million children suffer from malnutrition.
In the last few years, even before the civil war ended, oil revenues surged in Angola with companies such as BP, ExxonMobil and Total expanding operations. Those funds totalled $17.8 billion from 1997 to 2002, or about 85 percent of government revenue, the Human Rights Watch report said.
But an IMF analysis quoted by Human Rights Watch showed $4.22 billion had gone missing, or roughly 9.25 percent of Angola's gross domestic product (GDP) annually.
In those same years, total social spending in the country, from the government or from private or foreign sources amounted to $4.27 billion, the report said.
Angola is Africa's second largest oil producer after Nigeria. Although it produces around 900,000 barrels of crude oil per day most of its 13 million people still live on less than a dollar a day.
Human Rights Watch urged donors to make aid to Angola conditional on "strict" transparency in the government budget.
In response to previous criticism about corruption, Angola's ambassador in Washington, Josefina Pitra Diakite, last month said the government intended to increase social spending to 33 percent of the budget and was taking steps to reform its economy and disclose more revenues.