Russian oligarch Mikhail Fridman resigned as chief executive of oil producer TNK-BP, a joint venture with BP which has repeatedly clashed with the billionaire, the company said in a statement on Monday.
"Mikhail Fridman has submitted a letter of resignation to TNK-BP Ltd.'s board of directors, notifying his resignation from the position of chief executive officer of the TNK-BP Group," the statement said.
Fridman also resigned from the post of chairman of the management board of TNK-BP Management, TNK-BP Group's subsidiary which operates assets in Russia and Ukraine.
The resignations will take effect in 30 days, the company added.
TNK-BP is owned 50 percent by BP and 50 percent by a group of Russian billionaires known as Alfa-Acess-Renova (AAR) which includes Fridman.
The two other AAR shareholders -- German Khan and Victor Vekselberg -- stay on as executive directors and members of the management board, the company said without providing further details.
TNK-BP operation of huge oil fields in Siberia makes it one of the crown jewels for the British firm and accounts for a quarter of its total production.
TNK-BP has been dogged by boardroom disputes for the past few years. Last year, AAR prevented BP from completing a historic tie-up with state-owned Rosneft arguing that it would break their shareholder agreement.