Kenya's anti-corruption chief and four of his deputies are leaving office after President Mwai Kibaki signed a law establishing a new agency to investigate graft.

The revamped anti-corruption effort is part of the country's new constitution, and will feature new directors who will take office within three months.

Patrick Lumumba, the director of the Kenya Anti-Corruption Commission, is set to leave his post along with his deputies within a week.

Lumumba took the job in July 2010, and this year the commission has launched investigations into several top politicians. Foreign Minister Moses Wetang'ula, Industrialization Minister Henry Kosgey and powerful Rift Valley politician William Ruto all resigned their posts over corruption allegations.

But none of the commission's major investigations under Lumumba's tenure have resulted in significant convictions, and politicians who were forced to leave office have since returned to government.

Members of parliament have accused Lumumba of using his office to engage in political attacks. But Vice President Kalonzo Musyoka has defended Lumumba, saying the lawmakers were threatened by his “bold” fight against corruption.