The ruling Democratic Party of Japan and the conservative Liberal Democratic Party might shelve an electoral reform proposal that would cut proportional representation seats in the Lower House to prevent smaller political parties from shrinking, sources said Saturday.

The Supreme Court ruled in March that the current electoral system is "in a state of unconstitutionality" because a disparity was observed in vote weights in some districts during the House of Representatives election in August 2009. The vote weight disparity was as high as to 2.3 to one.

Both the DPJ and the LDP have pledged to reduce the number of proportional representation seats — by 80 and 30, respectively — to narrow the disparity.