A government panel has urged Norinchukin Bank to diversify its bond-heavy investment portfolio after the country’s largest agricultural lender racked up huge losses on foreign debt holdings.

The committee advised the bank to increase members of its board with experience in financial markets, including from outside the organization, according to a report released Tuesday.

"One of the causes of the losses was that the portfolio was too concentrated on bonds,” the panel said. "Norinchukin should consider diversification of the portfolio while building up proper risk management and introducing outside expertise.”