"Recently Taiwan authorities have urged Taiwan's post company to stamp letters with the postmark "Taiwan enters the United Nations' in Chinese and English," said Fan Liqing, spokeswoman for China's Taiwan Affairs Office.
"This is brazenly using the postal service to engage in propaganda advocating Taiwan independence."
Mainland post offices have been ordered to return all mail with such postmarks back to Taiwan, she said.
Fan did not elaborate on how much mail had already been returned, but said all consequences of the returned mail must be borne by the Taiwan authorities.
"This is a violation of the right of Taiwanese people to freely communicate and has severely influenced the communications between the two sides of the strait," Fan told journalists.
The Taiwan Post Co. said 152 letters stamped with the mark were returned between October 1 and November 13 from China.
It said the mark only goes on the letters of those who agree to have it, adding that the postmark will remain available until December 31.
Taiwan, under its official name the Republic of China, lost its UN seat to China in 1971. Its efforts to rejoin using its official title have been repeatedly blocked by Beijing, which sees the island as part of its territory.
Beijing fears that Taiwan's independence-minded President Chen Shui-bian will push ahead with a referendum on UN membership for the island under the name "Taiwan."
Taiwan split from the mainland following civil war in 1949 and since then China has refused to acknowledge it as a separate country and has vowed to retake the island by force if it ever formally declares independence.
Güncelleme Tarihi: 14 Kasım 2007, 10:13