BEIJING, November 4 -- Taiwan's major opposition party on Saturday staged a mass rally in the island's southern city of Kaohsiung, demanding Taiwan leader Chen Shui-bian to step down as his corruption-tainted family sank deeper in scandal.

As the worst political crisis facing Chen, the island's prosecutors on Friday indicted Wu Shu-chen, Chen's wife, over embezzlement, forgery, and perjury, involving 14.8 million New Taiwan dollars (448,500 U.S. dollars).

Wu was accused of claiming personal expenses from government funds. Prosecutors said Chen was also suspected of graft and forgery but as local leader he is immune to prosecution until his term expires in 2008.

Led by its chief Ma Ying-jeou, the opposition Kuomintang party on Friday afternoon took to the streets of Kaohsiung and surrounded the city government office. The protestors dressed in red and chanted anti-Chen slogans, according to Taiwan media reports.

Ma Ying-jeou called on the public to join in the march, saying that the corruption scandal surrounding Chen's family and his Democratic Progressive Party have brought the attention of the world, and Taiwan people should act out to end the graft-plagued government.

The march is scheduled to be staged on Sunday in Taipei, where Ma serves as the mayor.

Ma's party earlier Saturday said it will file a third recall motion to oust Chen next week, if he refuses to quit office.

In June and October, Chen survived two ousting motions as DPP "legislators" boycotted the vote and Taiwan Solidarity Union, a DPP ally, wavered in the "Legislature Yuan."

According to Taiwan regulations, only when two-thirds, or 148 votes, of the "legislature" approve the motion, could Chen be ousted.