Prosecutors in Taiwan are investigating a former vice premier and senior figure of the ruling Democratic Progressive Party on suspicion of bribery.

The prosecutors in the city of Taoyuan announced on Saturday that Cheng Wen-tsan is suspected of receiving bribes in connection with his official duties.

Taiwan media say the alleged corruption may involve a development project during his time as mayor of Taoyuan.

Cheng now heads the Straits Exchange Foundation, which is Taiwan's liaison office with China.

The foundation says Cheng issued a statement via his lawyer, stressing that he has not committed any illegal acts and will cooperate with the judicial investigation.

Cheng reportedly added that he hopes to clarify the truth and prove his innocence as soon as possible.

In June last year he made a visit to Japan, which is rare for a sitting Taiwan vice premier.

Taiwan's opposition parties, which hold a majority in parliament, have been arguing that the DPP is corrupt.

They have been working to expand the legislature's investigative authority through a legal amendment.

The opposition is expected to ramp up pressure on the government of President Lai Ching-te.