Diet discussions on whether to revise the Constitution began in earnest Thursday, with the Liberal Democratic Party proposing that reigning emperors be referred to as the head of state, rather than "the symbol of the state" as currently stipulated.

During a meeting of the Lower House commission on the Constitution, LDP lawmaker Gen Nakatani said emperors should be called the head of state because they represent Japan in diplomatic affairs.

But LDP ally New Komeito and two smaller opposition parties, the Kizuna Party and the Social Democratic Party, opposed the idea, saying there is more public acceptance in having emperors as the symbol of the state. Your Party, meanwhile, backed the LDP proposal.

The session marked the first full-fledged discussions on the Constitution since the commission and a similar entity in the Upper House launched their activities in November.

On Imperial succession, the SDP called for making it possible for a female to take the throne, and New Komeito was positive toward the suggestion.

Democratic Party of Japan lawmaker Ikuo Yamahana, meanwhile, called for a referendum on revisions to the Imperial House Law, such as allowing a female to take the throne.

The LDP and Your Party said the national flag and anthem must be stipulated in the Constitution, but this was opposed by New Komeito, the Japanese Communist Party and the SDP.

The flag and anthem are sensitive topics as critics say they are symbols of Japan's military past.

The commission will basically meet every week and study the Constitution's 11 chapters and the preamble. During their meeting next Thursday, members will cover Chapter 2, which renounces war.