Media reports that Emperor Akihito is hoping to abdicate triggered calls on Wednesday from ruling and opposition parties for work on revising the law to make it possible for a monarch to relinquish the throne while still alive.
"I think we need to revise the Imperial House Law," Tsutomu Sato, the head of the ruling Liberal Democratic Party's Diet Affairs Committee, told reporters, referring to the 1947 law that has no provision for a reigning emperor to abdicate.
"I want the matter to be discussed inside the party. We should deal with the issue cautiously," he added.
A senior official of Komeito, the LDP's junior coalition ally, said talks on revising the law should take place "swiftly" if the 82-year-old Emperor has already made up his mind.
Also echoing the need for discussions was Jin Matsubara, a former head of the National Public Safety Commission who belongs to the main opposition force, the Democratic Party.
Japanese Communist Party secretariat head Akira Koike declined comment, saying the Emperor's intention has not been "officially presented."
The leader of the Social Democratic Party, Tadatomo Yoshida, said he supports revising the Imperial House Law "as necessary."
"The most important thing is the health of the Emperor. It is desirable that he abdicates while he is in good condition to ensure a smooth Imperial succession," Yoshida said.
A government source said Wednesday that Emperor Akihito has expressed his intention to abdicate, sending shockwaves across the country, which for decades has seen Imperial succession only happen upon the demise of the reigning emperor.
The Imperial House Law's Article 4 says that "upon the demise of the Emperor, the Imperial Heir shall immediately accede to the Throne." But there is no provision in the law for an emperor to abdicate.