A House of Representatives committee on Friday endorsed a set of bills to cover a six-point plan aimed at improving the Lower House electoral system.
The ruling coalition — the Liberal Democratic Party, New Komeito and New Conservative Party — supported the bill, as did the Democratic Party of Japan, the main opposition force, and the Liberal Party.
The move has effectively paved the way for the new rules to be introduced before the next general election, which is expected to take place in late June.
The bills, which will revise the Public Offices Election Law, are expected to clear the Lower House plenary session Tuesday and become law as early as this month.
Among the proposed changes is a provision to ban the election of lawmakers to proportional representation seats if they run in the same election in a single-seat constituency and fail to win 10 percent of the vote there.
The reform was prompted by criticism that candidates are able to secure seats through the proportional representation system after failing to obtain the legally required number of votes in single-seat constituencies.
The ruling bloc had initially planned to ban the election of candidates who do not obtain the legally required number of votes — one-sixth of eligible votes — but lowered the requirement after some opposition parties rejected the idea.
The bills also include a ban on lawmakers seated through proportional representation from changing parties.
They also say Lower House by-elections should be held only twice a year, in April and October, rather than whenever a seat is vacated.