Katsuhiko Shirakawa, a former home affairs minister and ex-chairman of the National Public Safety Commission, has admitted visiting an illegal casino in Tokyo under a false name -- but has denied placing any bets.
Shirakawa, 58, ran in November's House of Representatives election in an attempt to regain his Diet seat, but was unsuccessful.
The facility in question has since been raided by police and closed down.
Shirakawa told Kyodo News: "I went three or four times using the name 'Yamamoto' but did not place any bets. There's no problem about just being in the casino."
Former casino employees spilled the beans on Shirakawa's visits in testimony adopted as evidence by the Tokyo District Court in the trial of the casino's 35-year-old former manager, who was convicted and handed a suspended sentence.
Casino gambling is banned in Japan.
In October, police arrested 34 people, including customers, the then manager and employees of the casino in Tokyo's Shibuya Ward. The manager and four others were later indicted.
The employees testified that Shirakawa had used the name "Yamamoto" in visiting the Shibuya J Club casino from last spring to summer, gambling for up to five hours a day. He allegedly lost around 2 million yen.
The casino earned about 90 million yen from October 2002 -- when it opened -- until it was shut down.
Shirakawa served concurrently as home affairs minister and as chairman of the National Public Safety Commission between November 1996 and September 1997 in the Cabinet of then Prime Minister Ryutaro Hashimoto.
He left the Liberal Democratic Party in February 2001 and established a new party, dubbed Shinto Jiyu To Kibo, or New Party Freedom and Hope. He lost his Diet seat in the House of Councilors election in July that year.