Pressure is mounting on Prime Minister Sanae Takaichi over reports that her aide was involved in posting videos on social media to disparage her rivals in the Liberal Democratic Party leadership race in October.

“Neither I nor my office has ever slandered or defamed other candidates,” Takaichi said on June 8 when asked about a media interview with a man who alleged that he created and distributed those videos at the behest of her campaign.

A Kyodo News report on June 7 quoted Ken Matsui as saying he proposed putting out “negative messaging” in an online meeting when Takaichi’s secretary in her constituency sought advice on how to overtake Shinjiro Koizumi, now her defense minister, in the LDP race.

Matsui said he used generative artificial intelligence to produce “between 1,000 and 1,500” videos targeting Koizumi and Yoshimasa Hayashi, now Takaichi’s internal affairs minister, and spread them on social media.

The report said the cellphone number used to exchange messages with Matsui was confirmed to belong to Takaichi’s aide.

Takaichi told reporters on June 8 that Matsui and her aide “have no personal acquaintance.”

Explaining what she meant by “personal acquaintance,” she said the two have never met in person, exchanged business cards or properly recognized each other’s affiliation or name.

Takaichi has maintained that she never asked a third party to create or distribute videos smearing other candidates since Shukan Bunshun broke the news at the end of April.

On June 3, the weekly magazine released an audio recording said to be exchanges between Matsui and the secretary during an online meeting.

Takaichi told the Diet that the voice identified as her secretary’s sounds “unnatural,” adding that it is “difficult to determine” whether it is her secretary’s voice.

Opposition parties have called for Takaichi’s aide to address the audio.

On June 9, Yoshitaka Saito, the Diet affairs chief of the Constitutional Democratic Party of Japan, asked that the secretary be summoned as an unsworn witness to the Upper House Budget Committee, which is scheduled to convene later this month.

However, Yoshihiko Isozaki, his counterpart from the ruling Liberal Democratic Party in the upper chamber, declined, saying it would be difficult.

After the meeting, Isozaki requested that these matters be addressed through exchanges with Takaichi, which Saito disagrees with.

“Having the secretary explain in the Diet is the quickest way to dispel doubts,” Saito said. “If there is a reason the individual cannot be called as a witness, that needs to be made clear.”

Takeshi Shina, secretary-general of the Centrist Reform Alliance (Chudo), emphasized the need to summon the secretary as an unsworn witness.

“It is odd that despite so vehemently denying involvement, (Takaichi) does not appear to be proactively working to uncover the truth,” he told reporters on June 9. “If she has nothing to hide, shouldn’t she take the initiative herself?”

At a news conference, Yuichiro Tamaki, leader of the Democratic Party for the People, also said it is important to give complete answers where doubts have been raised.

Opposition parties have also voiced criticism of Takaichi’s handling of the reports.

At a news conference on June 8, CDP leader Shunichi Mizuoka said the party intends to rigorously pursue the contradictions in Takaichi’s explanations.

Akira Koike, who heads the Japanese Communist Party’s secretariat, said Takaichi is making no genuine attempt to respond to the questions of the public and lawmakers.

“Her fitness to serve as prime minister is at issue,” he said.

Concern has been expressed even within the LDP.

“This is not something Takaichi can get away with simply by saying ‘I do not know,’” a former party executive said. “The issue will likely expand from here on out.”