Justice Minister Mayumi Moriyama was the focus of a Diet row Wednesday over alleged contradictions in her remarks over the death of a prison inmate that the opposition camp slammed as an attempt to cover the scandal up.

Moriyama has fallen into a predicament over her Diet responses regarding the December 2001 death a 43-year-old Nagoya Prison inmate. On Wednesday, the dispute led to demands by four opposition parties -- the Democratic Party of Japan, the Liberal Party, the Social Democratic Party and the Japanese Communist Party -- for her to step down, as well as threats to boycott Diet deliberations unless the government acts to resolve the matter.

The inmate died after guards allegedly subjected him to anal torture with a high-pressure fire hose, which left him with lacerations deep in his rectum. A 46-year-old deputy chief warden suspected of giving the orders for the abuse was arrested in connection with the case Feb. 12.