Takako Doi said Thursday she will resign as president of the Social Democratic Party to take responsibility for the SDP's crushing defeat in the general election.

Doi, 74, one of Japan's best-known female politicians, had long been the sole pillar supporting the pacifist party, whose fortunes have waned over the years, and a bulwark against moves to revise Japan's war-renouncing Constitution.

Although the minor opposition party had rallied around Doi, seeing the general election as a do-or-die situation for the SDP, it lost two-thirds of its seats in Sunday's election for the House of Representatives. It now holds six seats in the chamber.