The Corruption Investigation Office for High-ranking Officials(CIO) has booked main opposition People Power Party(PPP) presidential candidate Yoon Seok-youl for allegedly ordering the documentation of judges' traits on politically sensitive cases while he was chief prosecutor.

A local civic group that filed a complaint against Yoon and five others on charges of power abuse and violating the privacy law in June confirmed on Monday that the CIO had booked the candidate on October 22.

The group alleged that Yoon was responsible for the document, supposedly drawn up using illegal surveillance in February last year.

The group believes that the files were made to secure a favorable outcome for the prosecution in politically sensitive cases, such as the one surrounding former Justice Minister Cho Kuk.

Yoon is also accused of preventing investigations into the alleged documentation.

The CIO is currently investigating three other cases against Yoon, including one on alleged political meddling ahead of last year's general elections.