Japan's National Diet Building is seen in Tokyo. (Mainichi)

In 2016, the government discarded 444,877 documents slated to be saved for under a year and classified as specially designated secrets, the House of Representatives body overseeing the implementation of Japan's secrets law announced on March 28.

Government documents classified secret under the Act on the Protection of Specially Designated Secrets can, if they are set to be stored for less than a year, be disposed of by a simple process similar to the one applying to publicly available documents slated for retention for under a year. This system has led to worries that extremely important documents could be deliberately destroyed behind closed doors.

The government has apparently explained to the lower house Board of Oversight and Review of Specially Designated Secrets that the majority of the 444,000-plus special secrets disposed of in 2016 were "copies of extant originals, or documents with content included in other texts."

In 2017, it was revealed that the government had initiated procedures to dispose of 93 secret documents scheduled for retention for a year or more. Discarding such documents requires the approval of the independent Inspector General for Public Records Management and the Cabinet Office. However, items meant to be archived for less than a year need not go through this process, and it appears they are discarded at the discretion of the ministries and agencies holding them.

The lower house's oversight board examination of the conditions surrounding the over 444,000 discarded documents found that 413,313 were copies of still extant originals; 28,272 were the same as parts of other still extant documents; and 3,292 were related to codes.

In its 2017 report to lower house Speaker Tadamori Oshima, the secrets law oversight board demanded new rules restricting secret document storage periods of under a year to copies of still existing originals. It also called for the Inspector General for Public Records Management to examine any moves to dispose of such documents.