Chiu, 42, caught the public eye when television camera crews captured her powerful kick, which left a hole in Tseng's office door on April 19, as she and a group of DPP lawmakers attempted to barge in.

Footage of her kick was broadcast almost non-stop that day on various cable news channels, triggering widespread debate over whether or not it was proper for legislators to charge into government ministers' offices.

At issue was the abrupt transfer of former Taiwanese president Chen Shui-bian to a prison hospital by the justice ministry that morning, a move denounced by Chiu and her DPP colleagues as trampling on the former leader's human rights.

Chen, 62, who is serving a 20-year jail sentence for corruption, received medical treatment for serious depression and other ailments at a Taipei hospital.

After his treatment ended on April 18, the ministry decided to relocate him to a prison hospital in the central city of Taichung instead of allowing him to convalesce at home, as suggested by a doctor.

Chou Yuan-hua, Chen's attending physician at Taipei hospital, said this month the former leader would present a suicide risk if he were returned to Taipei prison. He suggested that Chen be allowed to convalesce at home or be moved to a hospital closer to home, where he could benefit from family support.

The transfer caught Chen's family and supporters off guard, and they heaped scorn on his "early-morning secret transfer".

The ministry said in a news conference Taiwan laws did not provide for home-based convalescence for convicts. But an angry Chiu and other DPP lawmakers stormed the gathering, seizing the podium where deputy justice minister Chen Ming-tang was briefing reporters. They protested against the transfer, slamming the justice ministry as a "Kuomintang" ministry, and accusing it of shaming Taiwan.

Chiu and other DPP legislators later proceeded to Tseng's office on the third floor of the ministry's building, trying to demand an explanation from Tseng, only to be told by a secretary that the minister was not there. In response, Chiu kicked at the closed door, dislodging a wooden panel, and with the help of a colleague unlocked the door. Slurs including "chicken" or "coward" were used.

The incident prompted ruling KMT lawmakers to demand that Tseng "act tougher" and file charges against the DPP lawmakers for illegal behaviour. "I would have no choice but to denounce the justice ministry if no action were taken," said KMT legislator Lai Shyh-bao. KMT legislator Lu Hsueh-chang said legislators exercised their constitutional functions with limits and that legislative immunity would not necessarily apply outside sessions of the legislature.

Chu Jia-chi, director of the ministry's prosecutorial affairs department, said the group could face charges of interfering with public functions, vandalising public property and insulting a public office.

In response, Chiu said: "I have nothing to fear because I was exercising my duty as a legislator." She urged Tseng not to become a "hit man" for Ma, who was to blame for the ministry's reluctance to release Chen on medical parole.

DPP chairman Su Tseng-chang also came to Chiu's defence, saying that if the Ma government sued the legislators it would only result in serious conflict between the government and the opposition. The DPP caucus in the legislature also decided to counter-sue Tseng for "fraud" and "coercion" by pretending that he was not in the office and sending Chen to the prison's hospital.

Analysts said it would be hard for people to sympathise with a graft-prone ex-president and the incident only highlighted the DPP's past violent reputation.

"If it wants to return to power, the DPP should stop its double standards in rationalising its unreasonable behaviour and distance itself from the corruption-tainted Chen," said political analyst George Tsai Wei, a professor of the Chinese Culture University in Taipei.

The DPP ruled between 2000 and 2008, until Chen's graft scandals caused public resentment and resulted in Ma winning the presidential election in 2008.