The Liberal Democratic Party has questioned former Prime Minister Yoshiro Mori over the latest political funds scandal behind the scenes, but he has denied any involvement in the matter, LDP sources said Friday.

The ruling party, meanwhile, is considering punishing some executives of its biggest faction who are implicated in the scandal by advising them to leave the LDP, which is the second severest disciplinary action after expulsion, a senior government official said.

The LDP has come under intense scrutiny after some of its factions, including the largest one formerly led by the late Prime Minister Shinzo Abe, for years neglected to report some of its income from fundraising parties, instead using the money for slush funds.

Former Japanese Prime Minister Yoshiro Mori attends the ruling Liberal Democratic Party's congress in Tokyo on March 17, 2024. (Kyodo)

Mori, who headed the faction from 1998 to 2000 and from 2001 to 2006, is suspected of having come up with the scheme, while senior members of the group have claimed not to know when the slush funds began.

Due to Mori telling the LDP that he was unaware of the details concerning how and when the scheme started within the faction, the party, led by Prime Minister Fumio Kishida, has judged that the former political leader could not be implicated in the scandal, the sources said.

For now, the party has no intention of reinvestigating Mori, who headed the Tokyo Olympics and Paralympics organizing committee until he had to resign over sexist remarks in 2021, they added.

But opposition parties have demanded that Mori, who served as prime minister for around one year from April 2000, be summoned to parliament as a sworn witness, with the LDP suggesting the practice of operating slush funds may have been in place for over 20 years.

Kishida said at a parliamentary session on Thursday that Mori, an 86-year-old LDP heavyweight, "could be included" as a target of the party's investigation as "he is needed to clarify political responsibility."

Later Thursday, Kishida also told a press conference that the LDP, which has been in power for most of the period since its formation in 1955, is preparing to take punitive measures as early as next week against about 80 lawmakers in relation to the slush funds scandal.

Such a step would mark the biggest case of disciplinary action to be carried out by the party and, in terms of scale, would exceed the penalizing of 50 members in 2005 after they opposed a bill to privatize the state-run postal service under then Prime Minister Junichiro Koizumi.

Disciplinary action based on party rules comes in eight levels of severity.

Earlier this month, Kishida and some of the party's executives also questioned four senior members of the Abe faction at the center of the political funds scandal as part of procedures to determine the specifics of the envisioned punishments.

The senior government official said Kishida has criticized some Abe faction executives for failing to sufficiently reflect on their involvement in the matter that caused public distrust in the LDP.

The scandal, which came to light late last year, has helped push the approval ratings for Kishida's Cabinet down to their lowest levels since it was launched in October 2021, just before three by-elections to fill vacancies in the House of Representatives are held on April 28.

Depending on the results of the by-elections, LDP lawmakers could seek to oust Kishida as leader before the next general election amid speculation that he will dissolve the lower house ahead of the party's presidential race, which will take place sometime around September, pundits said.

Up for grabs are seats in the Tokyo No. 15 district, the Shimane No. 1 district and the Nagasaki No. 3 district, all of which were held by LDP lawmakers before they became vacant. The ruling party has yet to decide on candidates for Tokyo and Nagasaki.

In the capital's constituency, Tomin First no Kai, a regional party founded by Tokyo Gov. Yuriko Koike, is arranging to field the famous author Hirotada Ototake, sources close to the matter said.

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