Four major opposition parties agreed Monday to demand the resignation of Chief Cabinet Secretary Yasuo Fukuda over his suggestion last week that Japan could abandon its three nonnuclear principles.

Although the remarks in question were initially attributed by the media to a top government official, Fukuda on Monday admitted that he himself was responsible.

On Friday, Fukuda told reporters that the three principles — not possessing, bringing in or using nuclear arms — are as amendable as the Constitution.