A retired Taiwanese general came under fire on Friday after he allegedly claimed that Taiwanese and Chinese armies are both "striving for unification" during a recent trip to China.

Hsia Ying-chou, ex-vice chief of Taiwan's air force general staff and former president of the National Defence University, reportedly made the remarks while attending a seminar in China this week.

"Our Nationalist army and the Communist army may have different ideals but we have the exact same goal to strive for the unification of the Chinese people," he was quoted by the Taipei-based Liberty Times as saying.

China still considers Taiwan part of its territory awaiting reunification, by force if necessary, even though the island has governed itself after a civil war in 1949.

Ties have improved markedly since Beijing-friendly Ma Ying-jeou became Taiwan's president in 2008, but political and military issues remain sensitive for the former bitter rivals.

The main opposition Democratic Progressive Party (DPP), which has been wary of closer China ties, lashed out at Hsia and vowed to amend a law to revoke pensions for retired servicemen who "damage Taiwan's sovereignty."

"Hsia should have the guts to give up the pension from now on to go to China since he does not identify with Taiwan and even hurt Taiwan," said DPP lawmaker Chen Ting-fei.

A presidential spokesman told reporters that Hsia's remarks were unacceptable if proven true, as they hurt the military's morale and go against Taiwan's policy of "no unification" with China.

In a similar incident last year, Hsia drew criticism after he reportedly suggested that the island's military owed as much loyalty to Beijing as Taipei.