A US anti-slavery group yesterday filed a Dollars 1bn (Pounds 600m) lawsuit against Talisman, the Canadian oil company, alleging its operations in Sudan have contributed to an ethnic cleansing campaign against civilians in the country's south. The class action suit, led by a southern Sudanese church leader, also seeks an injunction to prevent Talisman from continuing to co-operate with the Sudanese government, which has been involved in a 20-year war with southern rebels.