The ruling Democratic Party of Japan voted Monday in an opposition-boycotted Lower House committee to back its legislation aimed at rectifying the national disparity in vote values, which is threatening the constitutionality of Japan's elections.

The bills, which are expected to clear a Lower House vote Tuesday, will help remedy the gap, which gives voters in less-populated rural areas greater balloting weight than those in crowded urban districts.

Monday's vote came about 18 months after the Supreme Court ruled that the vote-value imbalance in the 2009 Lower House election, which brought the DPJ to power, was "in a state of unconstitutionality."