Yukio Hatoyama, leader of the Democratic Party of Japan, criticized Prime Minister Yoshiro Mori on Thursday for attending a wedding in 1995 at which a gang boss was present.

“If this is true, it is a big problem,” Hatoyama said at a lecture at the Foreign Correspondents Club of Japan. “We have already branded him as inappropriate as a prime minister, but I think this will serve to reinforce that.”

The chief of Japan’s largest opposition party said the DPJ would carry out its own investigation into the matter.

“It would be extremely awkward if a leader (of the ruling party) was associated with (a gang boss) while the government was trying to create strict measures against gangster groups,” he said. “We will carry out investigations seriously.”

Chief Cabinet Secretary Mikio Aoki admitted Thursday that Mori did make a speech at the wedding, but did not know at the time Yuko Inagawa, head of the Inagawa-kai crime syndicate, was present.

“He made a speech but left soon after finishing it, and never took a seat. He was not aware who was present,” the top government spokesman told a news conference.

Aoki told a morning press conference that Mori found out about the presence of the gang boss “only after attending the wedding,” and that he did not check who would be present before he arrived.

Political sources said Mori, who was secretary general of the Liberal Democratic Party at the time, and several other LDP lawmakers were among the guests at the wedding held May 27, 1995, at a Tokyo hotel.

The bride and groom were both secretaries to former International Trade and Industry Minister Eiichi Nakao, an LDP member of the House of Representatives.

The other LDP members present at the wedding were former Home Affairs Minister Hiroyuki Kurata and former Education Minister Yutaka Inoue, as well as Lower House members Yasukazu Hamada and Kazuo Eguchi. Eguchi was not a lawmaker at the time of the wedding.