The Japanese government has approved legislation that will permit Emperor Akihito to abdicate the Chrysanthemum throne, becoming the first emperor to step down in more than two centuries.

The emperor is expected to abdicate in December 2018, when he will mark his 85th birthday, in favour of his oldest son, Crown Prince Naruhito.

His renunciation of the throne, however, does little to solve the crisis within the world's oldest monarchy.

The last Japanese monarch to renounce the throne was Emperor Kokaku, who stepped down in 1817, but Emperor Akihito's decision was initially met by opposition in some quarters.

Anticipating resistance from conservatives who wanted him to retain his position until his death, the emperor went public in August last year with only his second ever televised address to the nation, during which he expressed his desire to abdicate.