A former justice minister arrested for alleged vote-buying in connection with his lawmaker wife's election last year made what appeared to be an attempt to use cash to secure votes for himself in an election nearly 15 years ago, a former assembly member has said.

Katsuyuki Kawai visited the then assembly member's office before a House of Representatives election in September 2005 and tried to give him an envelope, saying, "You will help me in many ways," according to the man, who was a member of the assembly of one of the cities within Kawai's constituency in Hiroshima Prefecture.

The former assemblyman said he refused to take the envelope but believed it contained cash, adding that Kawai, who went on to be successful in the election, was alone when he made the visit.