The House of Representatives on Tuesday issued a congratulatory message to Emperor Akihito on his 30-year reign, ahead of his abdication at the end of April, in the first such message dedicated to a particular Imperial anniversary.

"We, the Japanese people, respectfully acknowledge His Majesty the Emperor's achievements over the past 30 years under his era of Heisei, during which he has always stood by the people and prayed for their peace," read the message adopted in the Lower House plenary session.

Among political parties, the Japanese Communist Party, which has traditionally maintained a distance from the Imperial system, boycotted the Diet session, saying the party does not agree with the "unprecedented" message that "excessively praises" the Emperor in light of the principle of popular sovereignty.