TOKYO • The Japanese government is considering a system whereby the royal status of former female members can be reinstated, thus allowing them to perform some official duties, sources told local media.

There is the option of commissioning official duties to married women who were from the imperial family, an aide to Prime Minister Shinzo Abe said.

This would avoid a debate on allowing the creation of female imperial branches of the world's oldest royal family, reported Japan Times, citing reports from Jiji Press and Kyodo news agency .

Concerns over the shrinking pool of royals in Japan were reignited following news of Princess Mako's impending engagement to her university sweetheart, Mr Kei Komuro.

Princess Mako, 25, is the eldest child of Prince Akishino, Emperor Akihito's second son, and, like all female imperial family members, loses her royal status upon marriage to a commoner under the Imperial Household Law.

The law does not apply to male royals, with Emperor Akihito and both his sons marrying commoners, who are now part of the monarchy.

After Princess Mako gets married, the number of imperial family members will drop to 18, of whom 13 will be women.

A panel of experts suggested last month that Tokyo should consider ways to allow female royals married to commoners to continue with official duties.

The main opposition Democratic Party strongly advocates a system that allows female members to establish branches of the family after getting married.

"We should look at the reality," Mr Yoshihiko Noda, the party's secretary-general, told a recent news conference. "Some say it shouldn't be used politically, but the responsible behaviour would be to debate based on reality."

A separate government source said the so-called commission option would not solve the issue of the dwindling number of royals qualified to ascend the Chrysanthemum Throne, reported Japanese media.

There are now only eight imperial family members aged below 40. Prince Hisahito, 10, son of Prince Akishino, is the only male among them.

Only male members are allowed to become emperor.

Commenting on the dwindling number of imperial family members during a news conference last November, Prince Akishino said it would be "difficult" to continue duties under the current system.

Talks to revise the patriarchal law to allow for female succession have been politically sensitive.

A debate that started in 2005 was quickly abandoned after Prince Hisahito was born the following year.