TAIPEI, July 28 (AP) -- Taiwan's opposition on Friday renewed a call for President Chen Shui-bian to resign, claiming a government auditing body has uncovered evidence that his office embezzled state funds.

Over the past four months opposition lawmakers have kept up a steady drumbeat of criticism against Chen for his alleged knowledge of scandals involving his family and inner circle, but this is the first time they have laid corruption charges directly at the president's door.

On Thursday, the Ministry of Audit said irregularities were found in the presidential office's accounting of expenditures from a secret fund that is normally used to support overseas diplomacy efforts.

It said a total of 36 million New Taiwan dollars (US$1.1 million; €900,000) of the presidential office's declared expenditure from that fund was not backed up with receipts.

The audit ministry has handed the case to prosecutors for further investigation, ministry official Wang Wen-hsing said.

The presidential office denied any wrongdoing, saying it is customary not to provide receipts from secret diplomatic operations.

But lawmaker Chang Hsien-yao of the opposition People First Party said the new revelations had convinced him to bring impeachment proceedings against Chen.

"We will pursue this case thoroughly," Chang said.

Another opposition lawmaker, Sun Ta-chien of the Nationalists, said the ministry's findings are proof of wrongdoing.

"The presidential office has no doubt violated the law," he said.

Last month, Chen survived an opposition-backed move to recall him from office. Lawmakers of the ruling Democratic Progressive Party voted against the move, saying the president shouldn't be ousted unless he himself has been involved in graft.

Initial DPP reaction to the audit ministry's revelations suggested the party will continue to back him.

One lawmaker, Hsu Kuo-yung, said only "minor procedural defects" had been uncovered and that no officials pocketed any money.

The audit revelations follow a series of high profile scandals involving Chen's inner circle.

Earlier this month his son-in-law, Chao Chien-min, was indicted on insider trading charges involving a local development company. Chao has denied the charges.

In April opposition lawmakers accused first lady Wu Shu-chen of profiting from the transfer of an upscale Taipei department store to new owners. The President's Office has denied the accusations, but prosecutors are investigating.

Opposition lawmakers began to look into the secret diplomatic fund after a Taiwanese businesswoman living in Australia accused a close friend of Wu of acquiring invoices from her company, purportedly for Wu's personal use.