President Ma Ying-jeou, bowing to pressure from businesses, is bent on signing the ECFA, falling into China's plot of hijacking Taiwan economically to force unification, Lee said.

“This (ECFA) is the most serious mistake that Ma has made,” said Lee in a written message delivered at a forum on his behalf by Huang Kun-hui, chairman of the Taiwan Solidarity Union.

The former president had just recovered from a cold, and chose not to attend the forum on the impact of ECFA at the advice of the doctor.

But in his message Lee said Ma is back-pedaling on human rights and democracy in his domestic policies.

He is denying Taiwan's status as a sovereign country, and turning it into a “Taiwan region” under a “one China” framework, Lee said. He urged Ma to listen to the public opinions, rather than China's.

He said the country's future will need a new constitution truly based on the people's opinions.

But presidential spokesman Tony Wang said the ECFA is aimed at revitalizing Taiwan's economy.

Wang said everyone in the democratic country has the right to speak up, and the Presidential Office respects Lee's views. While still president, the pro-independence Lee in the late 1990s said spelt out a so-called “two states theory,” describing China and Taiwan as having special state-to-state relations. China, angered by the theory, suspended cross-strait dialogue. But tensions across the strait have eased since Ma became president last May.

KMT Deputy Secretary General Chang Jung-kung said Lee's “two states theory” has failed.

He said Lee has also failed to adjust his views on cross-strait relations in line with the current trend.