Prosecutors pressed additional charges against a confidant of President Lee Myung-bak Wednesday as they wrapped up a reinvestigation into allegations authorities illegally spied on civilians critical of the government.

Former Vice Knowledge Economy Minister Park Young-joon, once considered a right-hand man of the president, is already under arrest in a separate corruption scandal. He was newly charged with ordering illegal spying on officials of the Ulsan city government connected with an industrial complex project when he was a presidential aide in 2008.

Four others were also indicted for their alleged involvement in the illegal surveillance operations, but the outcome of the three-month reinvestigation was seen as insufficient as it failed to clear suspicions that higher-level officials could have been involved.

Prosecutors launched the reinvestigation in March after one of the officials involved claimed the presidential office attempted to cover up the illegal operations. On Wednesday, however, prosecutors said they determined it "difficult to recognize" that the top office was involved.

In the original investigation, seven officials were indicted for allegedly spying on a businessman who had posted a video clip criticizing the Lee government. Three of those had new charges added Wednesday, in addition to Park and one other new suspect.

A key point of the inquiry was to find the source of 50 million won (US$42,798) that was given to the whistle-blower in the form of bundles of newly-printed cash. The cash bundles, which are not commonly seen in public, raised suspicions it was the government that attempted to silence the official.

Prosecutors said Wednesday they had failed to find the source of the cash.

The scandal centers on suspicions an anti-corruption team under the Prime Minister's Office recklessly collected information on not only government officials, but also civilians considered critical of the government, such as labor union leaders and reporters at unfriendly media firms.

Opposition parties have called the case a Korean version of the U.S. "Watergate scandal."

The presidential office said later Wednesday it is "apologetic" former officials of the top office were involved in the scandal, and would make extraordinary efforts to prevent similar cases from happening again. (Yonhap)