Tony Hayward, the former head of BP who stepped down after the Gulf of Mexico oil spill catastrophe, is leaving his post on the board of its Russian joint venture TNK-BP, the company said Monday. Hayward, who came under huge criticism for his role in the clean-up of the oil spill, took on the role at TNK-BP as a BP-appointed director in July 2010 when Robert Dudley took over as head of the British energy giant. Hayward \"informed the board that he would step down from the TNK-BP board of directors in order to pursue other opportunities,\" TNK-BP said in a statement. \"The board accepted his resignation, while at the same time recognising the significant contribution Mr Hayward has made to TNK-BP\'s development,\" it added. TNK-BP is owned 50 percent by BP and 50 percent by a group of Russian billionaires. Its operation of huge oil fields in Siberia makes it one of the British firm\'s crown jewels but relations with its Russian partners have been strained over development of the business.