The board of the African Development Bank (AfDB) says it is standing by an internal investigation that has cleared its president, Akinwunmi Adesina, of improper conduct.

Adesina, 60, has been accused of favoritism, corruption and nepotism in the running of the affairs of the Côte d’Ivoire based bank.

A group of unidentified whistle-blowers have accused the former Nigerian Agriculture minister of handing contracts to acquaintances and appointing relatives to strategic positions at the bank.

Adesina is due for re-election in August.

The United States thinks differently

Two weeks after the bank’s ethics committee found no evidence to support allegations of favoritism leveled against Adesina, the U.S. called for an independent probe.

The U.S rejected the bank’s investigation over reservations about the integrity of the internal process.

Nigeria has hit out at the U.S for calling for an independent probe, a move that violates the bank's rules.

President Muhammadu Buhari, prominent Nigerians and several African presidents have thrown their weight behind Adesina in the wake of the U.S' call for an independent probe.

However, the bank says it will carry out an independent review of the report in the interest of due process.

In a statement, AfDB’s board of governors said it believed the bank’s ethics committee, which produced the report, had carried out its role correctly.

“The independent review shall be conducted by a neutral high caliber individual with unquestionable experience, high international reputation and integrity,” AfDB said in a statement.

The AfDB board said the review of the investigation will take no more than four weeks and that it will not interfere with the bank’s electoral calendar.

The bank’s whistle-blowing and complaints handling policy will also be reviewed at a later date to ensure it is being properly implemented, Reuters reports.