A second letter sent by Taiwan's President Chen Shui-bian requesting UN membership was ignored Wednesday by the UN secretary general and the Security Council as China derided Chen as an "international troublemaker," according to dpa. China's UN Ambassador Wang Guangya, who held the rotating presidency of the Security Council in July, told Chinese journalists that he received Chen's letter and returned it on Tuesday, the last day of his presidency. Chen's "petty trick of sending a second letter is an extremely grave separatist move aimed at Taiwan independence and has once again exposed himself as a downright international troublemaker," China's state media Xinhua News Agency quoted Wang as saying. China is the "sole legitimate representative" of the UN, Wang said. "China's representation naturally covers Taiwan." Ban's spokesperson, Marie Okabe, said the second letter was returned to its senders and would likely elicit no response from the UN. "I cannot confirm at this point whether an official response has gone back yet, but our position has not changed," she said. Chen's first letter on July 20 requesting UN membership for Taiwan's 23 million people was ignored by Ban, but his legal counsel wrote back to say the UN is abiding by the so-called one-China policy, by which the UN General Assembly recognizes China as the only representative in the international organization. Chen sent a second letter Friday, which like the previous one, was endorsed by ambassadors whose countries are allied with Taiwan. Chen criticized Ban for taking on himself the decision to turn down a membership request, insisting the decision belongs to the 192-nation assembly and the UN Security Council. Both letters were sent to Ban and Guangya as president of the Security Council. China has threatened military action if Taiwan declares independence. Okabe acknowledged that the decision on UN membership belongs to the Security Council and General Assembly and is not Ban's, but said the assembly's decision to expel Taiwan from the organization meant the letter should be returned. "That's correct, it's up to the member states to decide on the membership of the UN," Okabe said. But "in keeping with Resolution 2758 of the General Assembly, it (the last letter) could not be received, and was returned by the legal office." Resolution 2758 in 1971 recognized the People's Republic of China as the sole UN member and expelled the Republic of China - Taiwan's official title - which held the UN seat since the founding of the UN in 1945. That resolution has been invoked by Beijing and the UN each time Taipei requested membership in the World Health Organization and United Nations. The island nation has tried since 1993 to break out of its international isolation by requesting UN membership as the Republic of China on Taiwan, but without any success. This year, it for the first time submitted its request under the name of Taiwan. In his first letter, Chen said, "The absence of Taiwan in the United Nations creates a gap in the global network for cooperation, goes against the ideals and notion of justice upheld by the United Nations, and moreover is ironic in light of the UN principle of universality."