The ruling Liberal Democratic Party's largest faction is believed to have underreported revenue from its fundraising events to reimburse its members for more than a decade, the LDP's internal investigation showed Thursday.

Prime Minister Fumio Kishida speaks to reporters at the premier's office on Feb. 15, 2024. (Kyodo)

The recipients used the funds for social gatherings, personnel expenses, vehicle purchases and other purposes, the report on the probe said, although it did not reveal the lawmakers' names or their expenditure amounts.

The report also said 32 party members were aware that the money was passed back from their faction and that 11 of them noticed it was not listed in their political funds document, adding that lawmakers belonging to the largest group appear to have received it in cash form.

An investigation team of the LDP, headed by Prime Minister Fumio Kishida, questioned 91 lawmakers and officials of intraparty groups, some of which have decided to disband after the slush funds scandal broke late last year.

Kishida told reporters later Thursday that he will "continue to urge" LDP lawmakers involved in the scandal to "be accountable," with the report saying it is necessary to toughen penalties for political funds-related misconduct within the ruling party.

Kenta Izumi, chief of the main opposition Constitutional Democratic Party of Japan, lambasted the LDP report, saying, "It doesn't say anything important and it's a sloppy investigation."

A separate survey released earlier this week said 85 out of 384 LDP members, including 10 candidates for the next general election, have underreported revenues in political funds documents.

But opposition parties have faulted the previous survey for failing to inquire how the unreported funds were used by LDP lawmakers, such as members of its largest faction, formerly led by the late Prime Minister Shinzo Abe.

The LDP has come under intense scrutiny amid allegations that three factions, including the one headed by Kishida until December, neglected to report portions of their incomes from fundraising parties and accumulated slush funds.

A total of 10 individuals belonging to the three groups have been indicted or issued summary indictments by prosecutors. Executives of the factions, however, have not faced criminal charges due to a lack of evidence implicating them.

In January, the LDP laid out internal reform proposals to strengthen its governance that pledged to move away from factions as vehicles for securing funds and allocating major government and party posts for lawmakers.

In response to a request by the opposition bloc to agree to hold a committee on political ethics in the House of Representatives, Kishida has instructed the LDP to arrange such a meeting, a source close to the matter said.

On Thursday, Koichi Hagiuda, a key member of the Abe faction, said he would attend the committee if the right conditions are met. The lawmaker, who resigned as LDP policy chief in December, admitted failing to report around 27 million yen ($180,000) for five years through 2022.

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