The International Finance Corporation, the World Bank’s private sector lending arm, has toughened rules for staff engagement with client companies after controversy over the way two executives jumped to groups that had received investments from the body.

Thierry Tanoh, former IFC vice-president for Latin America, sub-Saharan Africa, and Western Europe, became chief executive designate of Ecobank Transnational (ETI) the day before the IFC announced an increase of $100m in its investment in the pan-African bank.

Separately, Lars Thunnell, the IFC’s recently departed chief executive, was appointed last year to a position on the board of Kosmos, the Texan oil company that has spearheaded exploration for Ghana’s offshore oil with a blend of private equity and IFC backing.