TOKYO — Japan's struggling prime minister today called for national elections next month following a crushing defeat for his party in a Tokyo municipal election seen as a barometer of voter sentiment.

With the opposition surging in popularity — on the back of economic malaise and several gaffes by the ruling party — it appeared increasingly likely it could take power after 50 years of almost exclusive rule by Prime Minister Taro Aso's Liberal Democratic Party.

Aso told leaders of his party he would likely dissolve the powerful lower house of the legislature next week, with a general election to be Aug. 30, according to a party spokesman.

The emboldened opposition, led by the rising Democratic Party of Japan, added to his headaches today by submitting to parliament a no-confidence motion, said party spokesman Toshiaki Oikawa. The motion was expected to have little real effect other than to embarrass the administration and delay discussions on pending bills.

The political maneuvers came after elections results released early in the morning showed Aso's Liberal Democrats and their ruling coalition partner lost their majority in the Tokyo Metropolitan Assembly, the local parliament for Japan's capital and most populated prefecture. The opposition made major gains.

The Liberal Democrats began faltering a couple years ago and have seen a revolving door of prime ministers — Aso's two predecessors each lasted less than a year.