Akinwumi Adesina, 60, the former Nigeria minister of Agriculture became the first Nigerian to chair the AfDB in 2015.

A 15-page report earlier this year claimed that under his watch, the bank had been tarred by poor governance, impunity, personal enrichment and favouritism.

The panel of three experts, led by Robinson alongside Gambia's Chief Justice Hassan Jallow and the World Bank's integrity vice president Leonard McCarthy, cleared Adesina of all charges alleged by whistleblowers.

"The panel concurs with the committee in its findings in respect of all the allegations against the President and finds that they were properly considered and dismissed by the Committee," Monday's report concluded.

The rollercoaster of allegations has battered the African banking institution and Adesina -- who is the sole candidate for the bank's August's presidential elections -- after the whistleblowers' complaints were leaked to the media in April.

The former Nigerian finance minister had always stated he was "innocent" of the charges.

Robinson -- who led Ireland from 1990 to 1997 before serving as the United Nations High Commissioner for Human Rights until 2002 -- dismissed the 16 whistleblower allegations against Adesina.

The panel did not investigate the charges themselves, as that was not within their mandate.

The AfDB plays an important if largely behind-the-scenes role in African economies, financing projects in agriculture, health, energy, education, transport and other development sectors.