A half dozen opposition parties on Friday filed a joint motion urging a Diet lawmaker to resign for alluding to the possibility that war with Russia was the only way to regain control of the disputed islands off Hokkaido.

The motion in the House of Representatives was backed by six parties, increasing pressure on Hodaka Maruyama, who was ousted from Nippon Ishin no Kai on Tuesday, to quit after drawing a barrage of criticism for the remark.

Maruyama is refusing to leave and even if the Lower House passes the motion, it will not be legally binding.

He has "tarnished the authority and the integrity of the Diet as a whole," the motion stated.

The parties also asked the ruling bloc, led by Prime Minister Shinzo Abe's Liberal Democratic Party, to support the motion.

Maruyama uttered the remark during a recent visit to one of the four islands with a group of former residents from Japan. The group was making the visit under a visa-free exchange program between Japan and Russia.

According to people who traveled with him, Maruyama, who was drunk, asked Koyata Otsuka, the 89-year-old head of the group, "Do you think there is any alternative to war (to recover the islands)?" Otsuka dismissed the idea.

The remarks came amid continued negotiations with Russia to resolve the long-standing territorial issue, which has prevented the two countries from signing a post-World War II peace treaty.

The islands were seized by the former Soviet Union following Japan's surrender in August 1945.

Russia has argued the seizure was a legitimate outcome of the war.

Abe, who has made the return of the islands one of his top priorities, is seeking a breakthrough in talks with President Vladimir Putin.