Ex-premier Abe, who stepped down due to ill-health in September, is under fire after sources told media his office helped cover the costs of dinner parties for supporters, a possible violation of funding laws that conflicts with Abe's vehement denials in parliament last year.
Abe himself has been asked by Tokyo prosecutors to appear for voluntary questioning about the issue, media reported later on Thursday. Politicians in Japan are forbidden to provide anything to constituents that could be construed as a gift. The rule is so strict that two ministers in Abe's cabinet last year had to quit in quick succession for giving things such as melons, crabs and even potatoes to voters in their constituencies.