Taiwan's radical pro-independence party the Taiwan Solidarity Union (TSU) said Tuesday it would expel its former party chief after his controversial visit to China.

Shu Chin-chiang, who was TSU chairman from January 2005 through December 2006, joined a delegation accompanying the island's former vice president Lien Chan on a trip to China last month.

Lien, who paved the way for the current detente when he was the Kuomintang party's chairman in 2005, met President Xi Jinping.

According to a TSU statement, during the visit Shu hailed Lien as "the initiator of peaceful development across the Strait", and urged the major opposition Democratic Progressive Party (DPP) to remove "Taiwan independence" from its party platform.

"What he did and said has severely damaged the party's image and violated the party's established position that strives to safeguard Taiwan's sovereignty," the party said in the statement.

The TSU has only three seats in the 113-seat parliament while the DPP has 40 and the Kuomintang 64.

The TSU and the DPP have repeatedly accused the China-friendly Kuomintang party of trading Taiwan's interests to Beijing in exchange for marginal economic benefits, an allegation flatly rejected by the Kuomintang.

Cross-strait ties have improved markedly since 2008 after the Kuomintang's Ma Ying-jeou won the presidency on a platform of strengthening trade and tourism links. He was re-elected in 2012.

But despite the fast thawing tensions, China has refused to renounce the use of force against Taiwan should the island formally declare independence.

The two sides split in 1949 when the Kuomintang (Nationalists) fled to Taiwan after losing a civil war on the mainland.