The four opposition parties made good on their threat and jointly boycotted all Diet proceedings Wednesday to protest the ruling bloc's decision to extend the current Diet session to July 28.
The 40-day extension was formally approved Tuesday by the House of Representatives thanks to the majority held by the ruling coalition.
However, the opposition's hardline stance has thrown a wrench into the deliberation schedule for a government-sponsored bill to dispatch Self-Defense Forces elements to help in the reconstruction of Iraq.