The white paper, entitled Defense of Japan 2015, was passed after the ruling party rejected a previous draft that failed to mention China’s drilling activities, Kyodo news agency reported.
The new text said the platform, allegedly for natural gas extraction, was constructed too close to the median line between the Chinese and Japanese coastlines in the East China Sea and could be used for military purposes, according to the outlet.
It cited diplomatic sources as saying that the number of Chinese natural gas development platforms along the line has grown to 12 since 2010.
Relations between China and Japan have been strained due to a territorial dispute over the Spratly Islands in the South China Sea, an archipelago suspected of holding large oil and gas reserves.
Earlier this month, Japan alarmed China when the lower house of its parliament endorsed a new defense strategy that will allow Tokyo to send its troops abroad for the first time since World War II. The bills now need the support of the upper house.
