Tsai asked the government not to import U.S. bone-in beef and controversial beef products like offal and ground beef before the proposed talks begin.

"If the Ma (Ying-jeou) administration can't do that, we shall ask them to step down, " Tsai said in her address to the protesters. The decision by the government to allow the beef products to be imported has ignited strong criticism mainly from the opposition and people concerned about mad cow disease.

The march, aimed at voicing public opposition against the government's move, began Saturday at the Dinghao commercial square in downtown Taipei City. Former DPP chairmen Yu Shyi-kun and Frank Hsieh, both having served as premier in the DPP-led government between 2000 and 2008, participated in the parade.

Tsai accused the Ma government of having never discussed with the legislature, opposition parties, and people in the country about how it would handle the U.S. beef import issue.

"The government is not transparent, " she said, accusing the Kuomintang (KMT) -led government of violating the principles of democracy and transparency.

Tsai denounced the KMT for retracting its promise at the Legislative Yuan to write a law to prohibit the imports of high-risk U.S. beef and beef products. On the contrary, she said, the ruling party wants to turn the U.S.-Taiwan beef protocol signed by Taipei and Washington on Oct. 23 into "Municipal Law," she claimed.

The protest attracted around 20,000-30,000 people, according to the organizer. The 3.2-kilometer-long march took the participants to Zhongxiao East Road, Linsen South Road, Renai Road before reaching its destination at Ketagelan Boulevard.

During the parade, Frank Hsieh blamed President Ma for being the one that "sold out" Taiwan.

Defending his government's decision to further relax ban on U.S beef imports, President Ma has said that the lifting of the ban represented the removal of a major barrier between Taiwan and the United States.

As part of efforts to smooth the public's fear of bovine sponiform encephalopathy (BSE) or mad cow disease, the Cabinet-level Department of Health has put forth a series of screening measures to help bar the imports of U.S. beef offal and ground beef that are considered to be potentially hazardous to human health despite the lifting of the ban.

In related news, the non-profit Consumers' Foundation urged consumers to endorse a campaign it launched together with the Homemakers' Union and Foundation to put forth a referendum on demanding for restarting talks on the U.S. beef import protocol.

As of Friday, 74,358 signatures have been collected, nearly reaching the 86,000 signatures required for a public referendum to be held, according to Consumers' Foundation statistics. The foundation's chairman Hsieh Tien-jen said Saturday that they have assessed they need at least 120,000 signatures for the campaign to be successful, after deducting invalid signatures.

Taiwan lifted a ban on U.S. bone-in beef, as well as offal and ground beef from cattle younger than 30 months on Nov. 2.

Taiwan banned U.S. beef in 2003 when a case of mad cow disease was diagnosed in Seattle. The ban was lifted in April 2005 to allow imports of U.S. de-boned beef from cattle under 30 months, but the government reimposed the ban two months later when a second BSE case was discovered in the U.S.

In 2006, the DOH agreed to allow beef imports once again, but only boneless beef from cattle younger than 30 months, produced by certified slaughterhouses and without any risky parts.

(By Wen Kuei-hsiang, Yang Su-min & Elizabeth Hsu)