House of Representatives Speaker Tadamori Oshima on Friday tied Yohei Kono's record of 2,029 days spent serving in the role.
The 74-year-old took up the post in April 2015, succeeding Nobutaka Machimura, and was reappointed after the 2017 Lower House election.
"He has exercised his leadership on many occasions as a House of Representatives speaker, and also contributed to the development of democracy in Japan by leading the legislature," Chief Cabinet Secretary Katsunobu Kato said, congratulating Oshima.
Representing his Aomori Prefecture constituency for 12 terms, Oshima has served in various key government posts including education minister, secretary-general of the ruling Liberal Democratic Party and as the party's Diet affairs chief.
Holding a news conference to mark the achievement, Oshima called for the Diet, during the leadership of Prime Minister Yoshihide Suga, to reach a conclusion on how to ensure stable imperial succession as the imperial family continues to shrink.
"I have received reports that (the government) is well aware of the issue," said Oshima. "I hope that the Suga administration will reach a conclusion people can understand and relate to."
The number of imperial family members has been on the decline, and the 1947 Imperial House Law stipulates that only males members of the paternal line can ascend the chrysanthemum throne. Female members of the family have to abandon their imperial status if they marry a commoner.
As the Diet adopted a nonbinding resolution in 2017 asking the government to address the matter, Suga has vowed to do so — although he has not given a specific schedule for reaching a conclusion.
Currently, there are only three heirs to Emperor Naruhito, 60, who ascended the throne in May last year. They are his younger brother Crown Prince Akishino, 55, his nephew, Prince Hisahito, 14, and Prince Hitachi, his 85-year-old uncle.
