an supporting the island's bid to join the United Nations. Taiwan's post office began putting a "U.N. for Taiwan" postmark on some outgoing mail six weeks ago.
On Wednesday, Fan Liqing of China's Taiwan Affairs Council said letters and parcels bearing that slogan and one saying "Taiwan joining the United Nations" were being returned as a protest against alleged independence activities by the government of President Chen Shui-bian.
"As far as we know, the postal service departments of the mainland have already found mail from Taiwan sealed with ... writings such as 'Taiwan joining the United Nations' and have returned the mail back to Taiwan," Fan said at a news conference.
Since their split amid civil war nearly 60 years ago, Taiwan and China have confronted each other angrily across the 160-kilometer (100-mile) Taiwan Strait.
China regards the democratic island as part of its territory and has threatened to attack if it formalizes its de facto independence.
The rhetoric escalated this year when Chen's government started a campaign to win U.N. membership using the name Taiwan rather than its official title of the Republic of China.
The distinction is crucial because the Republic of China connotes continued support for the one China concept that has been at the core of China's Taiwan policy since their split in 1949, while the Taiwan title reflects support for the pro-independence stance of Chen's Democratic Progressive Party or DPP.
Fan said stamping mail with the slogans violated the freedom of communication of the Taiwanese people.
"The Taiwan authorities must take the responsibility for the consequences of this," she said.
Liu Te-shun, vice chairman of Taiwan's Mainland Affairs Council -- the Cabinet-level body in charge of implementing China policy -- said China's action contravened international mail practice.
"It is common for countries to stamp commemorative slogans on mail," he said. "The mail would then be delivered to recipients in accordance with freedom of communications."
China has expressed strong opposition not only to Chen's U.N. bid but also to earlier bids he has launched to emphasize Taiwan's separateness from the mainland.
Since scrapping a government body responsible for unification with the mainland early last year, Chen has systematically attacked the legacy of late president and unification icon Chiang Kai-shek, and stricken the China name from a number of government companies -- replacing it with Taiwan.
He has also pushed for far-reaching changes to school textbooks to de emphasize Taiwan's historical and cultural links to the mainland.
The moves have helped nourish a stronger sense of Taiwanese identity among some on the island, and come as Taiwan prepares to go to the polls in January to elect a new legislature, and a president two months later.
Chen cannot run again and his party's candidate, Frank Hsieh, faces the Nationalists' Ma Ying-jeou, who favors eventual unification with the mainland.
Ma, a popular former mayor of Taipei, has been trying to keep the spotlight on what he says is DPP incompetence in running the economy. However, Ma has been caught off balance by the debate over Taiwanese identity and the U.N. bid.
