Japan's major opposition Nippon Ishin Japan Innovation Party has picked co-head Baba Nobuyuki as its new leader.

Baba and two other Diet members, Adachi Yasushi and Umemura Mizuho, ran in the race to decide who will take over from current leader Matsui Ichiro.

In the leadership election, 586 special party members, including Diet and local assembly members, as well as 19,293 ordinary members, had one vote each.

Special party members cast their ballots at an extraordinary party conference on Saturday. Ordinary members voted by mail.

Baba garnered 8,527 votes, while Adachi won 1,158 and Umemura 1,140.

Baba, 57, is a fourth-term Lower House member. He became co-head of the party in November last year after serving as secretary-general for about six years.

During the campaign, he pledged to follow through with Matsui's policy of pursuing administrative and fiscal reform nationwide. Baba prevailed over the two other candidates, who called for reforming the party's management.