As part of its manifesto for this summer's Upper House election, the main opposition Democratic Party is considering a pledge to lower to 18 years old the age requirement to run for public office, party lawmakers said Saturday.

Currently, a candidate must be at least 25 years old to run in Lower House, mayoral and local assembly elections. To run for the Upper House or prefectural governorships, candidates must be at least 30 years old.

The DP push comes as the revised Public Offices Election Law, which lowers the voting age to 18 from 20, is scheduled to take effect June 19. The upcoming Upper House poll is likely to be the first national election that sees 18- and 19-year-olds casting ballots.

The DP, formed in February through a merger of the Democratic Party of Japan and the smaller Ishin no To (Japan Innovation Party), is expected to finalize its election pledge by the end of this month, the lawmakers said.

In a bid to boost the number of female lawmakers, the DP manifesto is also likely to introduce a new system in which Lower House candidates who have lost in a single-seat electoral district but are elected via proportional representation are picked in alternating male, female order, the lawmakers added.

Prime Minister Shinzo Abe's ruling Liberal Democratic Party by also plans to pledge to lower the minimum age for eligibility as a part of its campaign pledges.