Taiwan prosecutors indicted the island's China-friendly former president, Ma Ying-jeou, over the alleged leaking of classified information involving suspected influence-peddling by a powerful opposition lawmaker.

The Taipei District Public Prosecutor's Office found, after a six-month probe, that Ma broke laws on the protection of personal information, release of secrets and communications security and surveillance, office spokesman Chang Chieh-chin said on Tuesday.

The charges stem from a 2013 lawsuit brought by opposition legislative member Ker Chien-ming, who accused the then-president of leaking information taken from a wiretapped conversation, in which powerful Nationalist Party lawmaker Wang Jin-pyng pressed judicial officials to acquit Ker in a separate case.

Wang at the time was speaker of the legislature and Ma's main political rival within the ruling party.

Following the indictment, Ma told reporters in Taipei that passing on the information about suspected influence-peddling taken from the wiretap was not a criminal act.

"This was mainly about handling a crisis," Ma said. "I'm confident in my innocence."

His spokesperson Hsu Chao-hsin said "there's no way he should have been charged. Where is the justice?"

Divisive figure

The charges carry a maximum sentence of three years each.

Ma was barred in June from visiting Hong Kong under a state secrecy law restricting travel by former top officials for three years after leaving office.

Ma's case will stir emotions in Taiwan, where public opinion about his performance in office remains divided, said Raymond Wu, managing director of Taipei-based political risk consultancy, e-telligence.

A US-educated legal scholar, Ma, 66, was credited with substantially improving Taiwan's relations with rival China during his two terms in office from 2008 to 2016.

However, his push for ever-closer ties sparked a backlash, especially among young Taiwanese wary of China's intentions towards the island it considers its own territory to be brought under control by force if necessary.

That led to his Nationalist Party losing both the presidency and its parliamentary majority to the pro-independence Democratic Progressive Party in polls in January 2016.