Prosecutors demanded Tuesday an 18-month prison term for lawmaker Anri Kawai, who has been indicted on a charge of vote-buying ahead of last year's House of Councilors election campaign.

In seeking the prison term during her trial at the Tokyo District Court, prosecutors argued Kawai, 47, committed an "unprecedented malicious crime that jolted the foundations of democracy."

Kawai, a former member of the ruling Liberal Democratic Party, has pleaded not guilty. The trial is expected to conclude after the defense counsel's closing argument slated for Dec. 23, with the ruling possibly handed down in January.

According to the indictment, Kawai conspired with her husband, Katsuyuki Kawai, 57, a former justice minister, to violate election law by handing out ¥1.7 million ($16,000) in total to five local assembly members in Hiroshima Prefecture between March and June last year.

Prosecutors claim the money was a reward for securing votes for her in the July 2019 Upper House election.

Anri Kawai said in the trial that the money was, among other things, her way of congratulating them for their victories in a prefectural assembly election, rather than an attempt to buy votes.

She also said she was not involved in the cash handout to one of the five individuals.

Meanwhile, local legislators who admitted to receiving cash testified that they thought the Kawais were asking them to secure votes for Anri Kawai in the election.

House of Representatives member Katsuyuki Kawai has been tried separately over his vote-buying charges, in which he is accused of handing about ¥29 million to 100 individuals in total.

The couple left the LDP before they were arrested on June 18. Katsuyuki Kawai is known for his close ties with former Prime Minister Shinzo Abe and his successor Yoshihide Suga.