Political reform and the Liberal Democratic Party’s handling of its slush fund scandal took center stage in Prime Minister Shigeru Ishiba's first one-on-one debate with opposition leaders in parliament Wednesday.

Constitutional Democratic Party of Japan leader Yoshihiko Noda lambasted Ishiba’s initial decision to give the party’s formal backing to lawmakers involved in the scandal in the Oct. 27 Lower House election.

“Taxpayers' money destined for political parties might be paid to people who have engaged in actions akin to tax evasion,” Noda said Wednesday, asking Ishiba to provide further explanations on the party’s endorsements. “From the perspective of public sentiment, I find this totally incomprehensible.”

On the morning of the same day, the LDP officially announced it will not back 12 of the party members involved in the scandal. Among them are LDP heavyweights such as former party policy chief Koichi Hagiuda and former trade minister Yasutoshi Nishimura.

Additional measures on whether to endorse other reprimanded lawmakers set to run under the proportional representation block might be announced in the coming days.

In his response to Noda, Ishiba said decisions on the endorsements were made after lengthy internal discussions and careful consideration of various factors, including the views of local constituents.

“I have many feelings about (the lawmakers),” Ishiba said Wednesday, adding that the party might eventually reinstate these lawmakers as party candidates if they win the election. “We made a careful judgment knowing how hard it is for each lawmaker to run with their own means.

“We will leave the final judgment to the electorate,” he said.

Ishiba didn’t rule out the possibility of conducting another internal probe to shed more light on the scandal when Noda pressed the issue.

Recalling how the prime minister had said the LDP would consider another inquiry in the event new facts emerge, Noda pointed to three recent developments: reports of a slush funds scheme within the faction led by LDP senior adviser Taro Aso, an indictment against former LDP lawmaker Manabu Horii, and a court testimony by the former treasurer of the faction Prime Minister Shinzo Abe once led saying that one of the faction’s bosses had ordered the underreporting.

Noda also demanded an explanation from Ishiba over reports that the faction he used to head allegedly underreported funds.

“I must apologize if there were some clerical errors, but there’s no indication of wrongdoing or proof that anyone benefited from those actions whatsoever,” Ishiba said.

Answering questions from Democratic Party for the People leader Yuichiro Tamaki, Ishiba said the party might make use of "funds for political activities," as they are known, in the upcoming election.

In an agreement with its junior partner Komeito and Nippon Ishin no Kai in June, the LDP said it would consider disclosing the usage of these funds in 10 years’ time. Lawmakers can receive money from the party funds without any obligation to clarify how they were used.

During a news conference on Wednesday evening, Ishiba said the party might be considering a full-fledged abolition of the funds in the future, without offering any specifics on a time frame.

“Some people think the usage of these funds should be fully disclosed. I believe that’s an option,” he said. “In any case, we should use them in a way that doesn’t cause any misunderstanding among the public.”

Ishiba also said he will not host fundraising parties during his tenure as prime minister. His predecessor, Fumio Kishida, received a lot of criticism from opposition parties for hosting such parties in his Hiroshima constituency early on in his tenure.