Taro Aso, Japan’s prime minister, has announced plans for an August 30 general election that opinion polls suggest could mark the end of the divided and dispirited Liberal Democratic party’s long dominance over the world’s second largest economy.

The decision to go to the polls more than a month before required appeared intended to secure Mr Aso’s position in the face of an increasingly open revolt from party colleagues who blame the prime minister for a disastrous defeat in a Tokyo Municipal Assembly election on Sunday.