The main opposition Democratic Party, forced to find a new leader after the sudden resignation of Renho, is set to choose its new head on Sept. 1, party lawmakers have said.

The contest is predicted to be fought between two veteran lawmakers, Seiji Maehara, a former foreign minister known for his conservative views on defense and other issues, and Yukio Edano, a former chief Cabinet secretary backed by the party's liberal wing.

The date for the contest, including the Aug. 21 start of campaigning, was officially endorsed at a meeting of party lawmakers Wednesday.

Renho, who goes by just her given name, became the party's leader last September but announced her shock resignation after the party lost seats in the recent Tokyo assembly election.

An Upper House member, she had also faced scrutiny over her former dual nationality, although she insisted this had nothing to do with her decision to give up the leadership.

Maehara and Edano were both core members of the party's predecessor — the Democratic Party of Japan — and served in key Cabinet posts while the DPJ led the government for three years, before the Liberal Democratic Party returned to power in December 2012.

Maehara, who lost to Renho in the previous leadership contest, announced Wednesday his intention to join the race, while Edano already announced Tuesday his plan to do so, sources said.

Despite a recent plunge in the approval ratings of Prime Minister Shinzo Abe's Cabinet, the leading opposition party has yet to make inroads, with polls showing low public support.