Senior opposition lawmakers demanded Thursday that Ichiro Ozawa testify under oath in the Diet over his alleged involvement in falsifying political funding reports.

During a meeting of secretaries general and Diet affairs chiefs of both the ruling and opposition parties, Democratic Party of Japan Secretary General Katsuya Okada explained to his counterparts how he failed to persuade Ozawa, a former leader of the DPJ, to give unsworn testimony before the Lower House Political Ethics Council.

Ozawa agreed at one point last month to explain the scandal to the ethics council but later flip-flopped out of concern his remarks would be used against him in his upcoming trial.

"The remaining option is to push for testimony under oath," said Ichiro Aisawa, Diet affairs chief of the Liberal Democratic Party.

"It's time the DPJ goes on to the next step," said New Komeito Secretary General Yoshihisa Inoue.

Opposition parties except for the Social Democratic Party, a former ruling coalition member, support the idea of Ozawa testifying under oath in the Lower House. The DPJ and its junior coalition partner, Kokumin Shinto (People's New Party), oppose the idea.

Traditionally, parties need to vote unanimously to summon a witness to the Diet for sworn testimony.

"Because sworn testimony is grave, we (the DPJ) can't easily agree to it," Okada said. "I ask for your support in voting for a resolution to convene the Lower House ethics council."

The DPJ had threatened to vote for a resolution to summon Ozawa, who faces indictment over the scandal, to give unsworn testimony before the ethics panel if he doesn't appear voluntarily.

But it gave up on the idea after opposition parties refused to vote on a nonbinding resolution, saying it is meaningless when Ozawa has no intention of appearing before the panel.