Prime Minister Yoshihiko Noda is expected to face conflict in the Diet session that kicked off Tuesday as opposition parties prepared to grill him over his Cabinet appointments, most notably about short-term trade minister Yoshio Hachiro, who stepped down after making jokes about the Fukushima nuclear crisis that has forced tens of thousands of people from their homes.

"It is highly regrettable that recently a Cabinet minister resigned following inappropriate statements lacking compassion for disaster victims," Noda said during his first policy speech, which kicked off the special four-day session.

"I would like to take this opportunity to pledge once again that the Cabinet redouble its concerted efforts to bring the nuclear accident to a conclusion."