Yeh Sheng-mao, former director of Taiwan's Bureau of Investigation, was convicted of concealing documents and leaking secrets to then president Chen to cover up for him, the court said.

This was lighter than a previous sentence of 10 years in jail handed down by a district court as the high court ruled that Yeh did not make any profit from the crime.

Yeh was found to have warned Chen while he was in power that an international financial watchdog was investigating his family for suspected money laundering.

Chen, who left office in 2008, is serving a term of 17 years and six months on two convictions of bribery, with more trials pending on other charges including money laundering.

Chen insists that the legal action against him is a vendetta carried out by Taiwan's current Beijing-friendly government in retaliation for his pro-independence stance while in power.