South Korean President Lee Myung-Bak's wife will be questioned in writing by special prosecutors probing alleged irregularities in the purchase of a retirement home for her husband, officials said Monday.
The questioning of First Lady Kim Yoon-Ok comes at a sensitive time, with South Korea just weeks away from a presidential election on December 19.
Park Geun-Hye, daughter of assassinated military dictator Park Chung-Hee, will contest from President Lee's ruling New Frontier Party.
Prosecutors have already grilled Lee's brother and son, but assistant special counsel Lee Chang-Hoon said protocol dictated that Kim would not be required to appear before the investigation team in person.
"We have decided to conduct a written questioning of the first lady," Lee told reporters.
The probe is focused on alleged irregularities in the purchase of a plot of land on the southern edge of Seoul to build a retirement home for President Lee when he formally leaves office in January.
The lot was jointly purchased by the president's son, Lee Si-Hyung, and the presidential security service which would need to house its agents on the site.
But the cost was allegedly not split evenly, with suggestions that the security service paid too high a price for its share, while Lee's son got a below-market rate for the residential plot.
The president's wife and brother have been included in the investigation because of reports that they each loaned Lee Si-Hyung 600 million won ($550,000) to buy the lot.
The presidential Blue House has denied opposition claims of financial chicanery.
But in the face of mounting criticism, the president scrapped the whole project and decided to move into his existing private house in southern Seoul after leaving office.