Japan’s Prime Minister Sanae Takaichi appears to have sidestepped a potentially embarrassing political landmine by publicly backing a close aide accused in media reports of running a smear campaign against her rivals, while stopping short of flatly denying his possible role.

The allegations, first reported in weekly tabloid news magazine Shukan Bunshun, claim that members of her own camp produced videos critical of rival candidates during last year’s Liberal Democratic Party leadership race, including Shinjiro Koizumi, whom Takaichi subsequently appointed as defence minister.

Whoever won the LDP leadership contest was all but guaranteed to become Japan’s next prime minister, raising the stakes of any alleged dirty tricks operation well beyond routine internal party mudslinging.

Takaichi was quizzed by opposition politicians in the Diet on Monday about the Shukan Bunshun reports, which emerged in late April.

The video clips at the heart of the smear campaign, which were posted to social media, described Koizumi as “incapable” and “a puppet of hereditary politics”, drawing attention to his use of cue cards in a debate as evidence of incompetence.