South Korean President Park Geun-hye has hired a lawyer ahead of questioning by prosecutors over a snowballing political scandal that has engulfed her administration, her spokesman said on Tuesday.

Park, who would be the first sitting president to be interrogated in a criminal case, has seen her approval ratings plunge, with hundreds of thousands of protesters taking to Seoul's streets on Saturday demanding she resign.

The scandal centers on Park's shadowy confidant Choi Soon-sil, who is accused of using her ties with the president to coerce major companies to donate millions of dollars to non-profit foundations that Choi then used for personal gain.