Under a ministry ordinance in the Passport Law to be revised June 1, the government will begin issuing passports next month to children who were not registered at birth because they were born within 300 days of their parents' divorce and would have to take the family name of the divorced husband, the Foreign Ministry said Thursday.

However, despite the directive aimed at easing public criticism of the so-called 300-day provision, the passports cannot be issued under the surname of the mothers or their real fathers.

The Passport Division asked the public for opinions earlier this month about revising an outdated Civil Code provision that stipulates children born within 300 days of a woman's divorce should be considered the offspring of the former husband.

Of the 1,300 or so opinions sent to the ministry, 1,220 backed the use of the surname of the mother or biological father in the children's passports.

But a division official said the ministry has no choice but to use the family names of the former husbands, as stated in the Civil Code, in the absence of clear legal relationships between unregistered children and their biological fathers.

The Justice Ministry has recently told municipalities to start accepting registration applications for some children left unregistered because of the provision.

Lack of a birth certificate bars a baby from being put into the family registry and from being registered as a resident. Such registrations are necessary to obtain official government documents, including passports.

Since Japanese citizens must submit copies of their family register to the government in order to get a passport, unregistered children have been unable to obtain one.

In April, Foreign Minister Taro Aso told officials to make an exception for unregistered children as public pressure mounted for the Civil Code to be revised amid an increase in school excursions abroad.