Award-winning Chinese director Xie Fei has slammed China\'s system of film censorship as wasteful and arbitrary, urging censors in an open letter to issue clearer rules on banned topics. Xie, 70, won international awards for such 1990s films as \"Black Snow\" and \"Woman Sesame Oil Maker\", which was handed the top prize at the Berlin film festival. In the letter addressed to the state film bureau, he cited recent difficulties in getting film approvals by numerous prominent Chinese directors including Jiang Wen, Tian Zhuangzhuang, and Jia Zhangke. \"The state administrative methods and the censorship system that manages the film industry long ago lost its real social, economic, ideological and cultural significance,\" Xie wrote in the letter, posted on his microblog page Saturday. It \"has only become a corrupt black spot for controlling the prosperity of the cultural and entertainment industry, killing artistic exploration and wasting administrative resources\". Controls on the kinds of films Chinese directors can make were also leading to poor box office showings, he said, with Chinese viewers largely favouring foreign films produced by film makers without such restraints. Xie has long been an outspoken critic of China\'s censorship system and in recent years has refused to make new films because of it. He has been working as artistic consultant on a movie about the 1966-1976 Cultural Revolution including homosexuality as a theme, which has been awaiting the censors\' approval for four months, he said. Xie said China\'s film censorship should be based on laws and regulations that are linked to the constitutionally guaranteed right to free speech and the right to publish. \"We must recognise that the best way to administer the cultural industry is through law and through the market,\" the letter said. \"Today\'s film censorship system is not \'ruled by law,\' but still ruled by a system based on personalities that we long ago said should end.\" China\'s censors were still banning anything they consider to be a negative portrayal of the nation, he said. China\'s film market, set to become the world\'s second-largest this year, maintains a quota on the number of foreign movies that can be shown in the nation\'s cinemas.