Taro Aso, Japan's prime minister, has been forced to acknowledge that a family coal mine used prisoners of war as forced labour during the second world war.

Documents released last year by the Ministry of Health, Labour and Welfare at the request of an opposition Diet member confirmed that Aso Mining had used 300 British, Dutch and Australian PoWs as labourers at a mine in 1945. Mr Aso was a child during the war but headed Aso Cement, the flagship company, in the 1970s.