The minority leader of the Chamber of Deputies, Ndidi Elumelu, asked the African Development Bank (AfDB) council to stop harassing its president, Akinwunmi Adesina.
Adesina, a former Nigeria minister of agriculture, was accused of violating the bank's code of conduct before his re-election in August.
After an investigation by the AfDB ethics committee found him innocent of the charges, the United States, the bank's second largest shareholder after Nigeria, called for a retrial.
Elumelu, in a motion statement obtained by Channels Television on Tuesday, described the allegations against Adesina as "reinforced".
He asked the House to investigate the matter and also urged the federal government and all African leaders to intervene in the situation.
"If this type of witch hunt and unnecessary harassment is not controlled and discouraged, it can become a recurring decimal, destabilizing the stability that the bank has enjoyed for decades and the intended results in a steady decline," he said.
On Tuesday, President Muhammadu Buhari pledged his support for Adesina in seeking a second term.
Former President Olusegun Obasanjo and other African leaders also expressed their support for the president of the AfDB.