Taiwanese prosecutors questioned President Ma Ying-jeou late Thursday, a report said, following allegations that a legislator's phone was wiretapped in a widening political scandal that has gripped the island.

Ma, whose approval ratings have plummeted in the wake of the scandal, was questioned as a witness by the Taipei district prosecutors' office over claims a top prosecutor illegally leaked information to him about a sensitive case, the state Central News Agency said without elaborating.

Prosecutor General Huang Shyh-ming has been accused of leaking information about an influence peddling case implicating parliamentary speaker Wang Jin-pyng and lawmaker Ker Chien-ming of the opposition Democratic Progressive Party (DPP).

The information was obtained by a wiretap on Ker's phone and Huang is accused of illegally passing that information on to President Ma.

Prosecutors have insisted the wiretapping was legal. But the DPP has compared it to the Watergate scandal in the United States which resulted in the resignation of then-president Richard Nixon in 1974 -- something they have now insisted Ma must do.

The scandal has even created bipartisan anger against Ma's presidency in Taiwan's notoriously fractious parliament as well as on the island's streets.

Ma's popularity has also taken a severe hit, plunging to a dismal 11 percent in the wake of the deepening political scandal that has already seen two top officials resign, including his spokesman.

Thousands of people took to the streets of Taipei on Sunday, hurling shoes at Ma's portrait and calling on him to step down.

Ma had said Wang was "unfit" to head the parliament after he was accused of influencing prosecutors not to appeal the acquittal last year of Ker in a breach of trust case.

While Ma described the incident as "the most shameful day" in Taiwan's democracy, the accusations have been strongly rejected by Wang.

Ma's ruling Kuomintang (KMT) party has suffered two legal setbacks in its bid to expel Wang from the party in order to render him unable to continue as speaker.

Prosecutors were not immediately available for comment.