The Philippines has protested China's new passport design, which includes the image of a map of the entire disputed South China Sea.
Foreign Secretary Albert del Rosario on Thursday said it was unacceptable because it impinges on the sovereignty of the Philippines, which has claims to territories in the South China Sea.
"The Philippines strongly protests the inclusion of the nine-dash lines in the e-passport as such image covers an area that is clearly part of the Philippines' territory and maritime domain," he said, quoting a diplomatic protest sent to Beijing.
The so-called nine-dash lines take in about 90 per cent of the 3.5-million-square-kilometre South China Sea on Chinese maps.
The boundary was first officially published on a map by China's government in 1947 and has been included in subsequent maps, forming a key basis for Beijing's claims to the area.
Vietnam, Malaysia, Brunei and Taiwan also have overlapping claims to the South China Sea, which straddles key shipping lanes in the region and is believed to be rich in resources.
In December, the Philippines is hosting a four-party meeting with Vietnam, Malaysia and Brunei in a bid to resolve the territorial dispute.