TAIPEI - Taiwan's opposition on Thursday launched a drive to demand the release of former president Chen Shui-bian, who has been detained during his trial on corruption charges.

The Democratic Progressive Party (DPP) urged the public to join a "one-person-one-letter" campaign to make the request to President Ma Ying-jeou, Justice Minister Wang Ching-feng and Lai In-jaw, head of the Judicial Yuan -- which interprets the constitution and laws -- a party spokesman said.

"We call for an immediate end to the detention of former president Chen and for an immediate reform of the detention system which violates human rights," it said in a statement.

"Chen's long-time detention has not only impacted the judiciary's image and credibility but caused serious social division and confrontation which threatens Taiwan's democratic development," said the statement co-signed by leading academics including Taiwanese Nobel prize winner Lee Yuan-tseh.

The DPP said it would also contact diplomatic missions stationed in Taiwan and international human rights groups to solicit support for its demand.

Chen, who has been locked up since late December, has remained silent in recent court sessions in an apparent protest against his detention and trial.

The former president has already dismissed his lawyers to protest against what he calls a political witch hunt by the Beijing-friendly Ma administration which succeeded him.

Chen, who left office last year after a maximum eight years, stands accused of embezzling public funds, money laundering, taking bribes as well as influence peddling and forgery.

His wife, son, daughter-in-law, and brother-in-law have already been charged with various offences in connection with the far-reaching case which has captivated Taiwan for months.

Under Taiwanese law, there are no limits on how long Chen can be detained.