President Moon Jae-in welcomed the passage of a bill Thursday on facilitating the launch of a non-prosecution body tasked with investigating corruption among senior government officials.

He said it's "fortunate" that the way has been opened for the speedy establishment of the Corruption Investigation Office for High-ranking Officials (CIO), according to Cheong Wa Dae spokesman Kang Min-seok.

The president expressed expectation that the CIO will be formally set up at the start of 2021, he added.

Moon's message came a few hours after the National Assembly passed a revision bill intended to expedite the process of picking the head of the CIO, in a 187-99 vote.

The ruling Democratic Party (DP), which holds 174 seats in the 300-member parliament, spearheaded the passage in spite of strong protests by the main opposition People Power Party (PPP).

Under the new legislation, the ruling bloc would be able to choose an inaugural CIO chief, with the PPP's de-facto right to veto removed.

The establishment of the CIO, independent from the state prosecution service, was one of Moon's major presidential campaign pledges. It's part of a politically controversial drive to reform the prosecution often accused of having excessive power and authority.

Moon was quoted as stressing that the establishment of the CIO is a "long-cherished desire and promise to the people" for thorough investigation into corruption by those in power, including the president, and a corruption-free society.

Prosecutors are among civil servants subject to the CIO's probe over alleged corruption.

A CIO bill was approved in December last year and the legislation took effect in July. But its launch has been delayed amid political disputes over the choice of its first leader.

The DP has accused the PPP of being uncooperative. The conservative opposition party argues that the CIO could be used to cover up possible corruption, especially by presidential aides, as a tool to put pressure on the state prosecution service.

The idea of setting up such an investigative organization was first floated here in the 1990s. (Yonhap)