Democratic Party of Japan lawmaker Hisayasu Nagata finally revealed Friday what various media sources have already divulged -- that Dumont magazine executive Takashi Nishizawa gave him the fake e-mail suggesting a shady financial link between Livedoor Co. founder Takafumi Horie and a son of Liberal Democratic Party Secretary General Tsutomu Takebe.

Following a session of the House of Representatives Disciplinary Committee, executive committee members met and and voted unanimously to summon Nishizawa for sworn testimony, panel chief Tetsundo Iwakuni said. The date was set for April 4.

During the Disciplinary Committee session, LDP lawmaker Katsuei Hirasawa said Nishizawa's lawyer had told him Nishizawa has denied giving Nagata the e-mail.

"It is a lie that Nishizawa was not the middleman who gave me the e-mail," Nagata argued, without identifying the original source of the e-mail. It "is a 100-percent lie. I will say so at the risk of my political career."

After the session, Iwakuni said: "Through this morning's session, we have learned that there are clearly two statements that contradict one another. It is the Disciplinary Committee's duty to determine which is the truth."

During the two-hour question-and-answer session Friday morning, Nagata, in unsworn testimony, told the committee he was revealing Nishizawa's identity because, after discovering that the information from him was false, he felt he could no longer trust the executive.

"I believe that I am a victim in the sense that I was deceived by Nishizawa," Nagata claimed. "But at the same time, I am also the offender. I have no intention of saying I am only a victim nor do I have any intention of shifting my responsibility onto Nishizawa."

Nagata repeated several times that he had not paid the magazine executive for the information.

Nagata admitted he had not checked the credibility of the e-mail -- which was made to look like Horie had ordered staff to transfer 30 million yen to Takebe's son before the September general elections -- sufficiently before presenting it to a Budget Committee meeting in February.

"I believe I may have somewhat exaggerated" the depth of my investigation, Nagata reckoned, claiming he had taken Nishizawa at his word.

The DPJ punished Nagata by suspended his party membership for six months.

Later Friday afternoon, DPJ Diet affairs chief Kozo Watanabe criticized Nagata's explanation of the affair, saying his words rang hollow.