The Nigerian government has rallied support for the president of the African Development Bank, Akinwumi Adesina.
A letter by the Nigerian Minister of Finance, Budget and National planning, Zainab Ahmed, urged the board of the AfDB to ignore calls for an independent investigation of Mr Adesina.
Mrs Ahmed urged Kaba Niale, chairman of the AfDB board of governors, to follow laid down processes to protect and preserve the bank.
"The call for an independent investigation of the president is outside of the laid down rules, procedures and governing system of the bank and its articles as it relates to the code of conduct on ethics for the president," the letter reads.
In a petition by a group of whistleblowers, Mr Adesina was accused of 20 breaches of the bank's code of conduct, including "unethical conduct, private gain, an impediment to efficiency, preferential treatment, and involvement in political activities."
The group, which noted their allegations were in line with AfDB's whistleblowing policy, said these activities adversely affected the confidence and integrity of the bank.
The bank, however, found the allegations to be "frivolous."
Regardless, the United States government expressed "deep reservations about the integrity of the committee's process" and called for a fresh "in-depth investigation of the allegations."
In a letter dated May 22, 2020 to Ms Niale, the U.S. government, through the Secretary, Department of Treasury in Washington, D.C., Steven Mnuchin, faulted the decision of the committee to totally exonerate Mr Adesina of all allegations, saying it was not yet time to make such a declaration.
Mr Adesina in his response Wednesday maintained that he was innocent of all allegations of fraud leveled against him. He added that he believed a just, transparent and fair process would prove his innocence.
"I am confident that fair, transparent and just processes that respect the rules, procedures and governance systems of the Bank, and the rule of law, will ultimately prove that I have not violated the Code of Ethics of this extraordinary institution," he said.
He also promised to work with other stakeholders of the bank in its drive to fulfil the mandate of transforming and accelerating Africa's development.
On Thursday, the Board of Governors said the bureau must be allowed to carry out its duty and deliver Justice on the matter.
In her letter Thursday, Mrs Ahmed implored the bank to adhere to procedures in addressing the issue.
"As a bank we must uphold the rule of law and respect the governance systems of the bank," she said.
"If there is any governance issue that needs improvement, there can be considered and amendment proposed for adoption in line with laid down procedure."