The presidential office Cheong Wa Dae on Wednesday lambasted special prosecutors for leaking the schedule set for investigators to question President Park Geun-hye over her role in the corruption scandal that led to her impeachment, further clouding the prospects of the unprecedented inquiry.

Some media outlets reported on the day that Cheong Wa Dae and the probe team, led by Independent Counsel Park Young-soo, had agreed to the plan to question Park face to face at her presidential office on Thursday.

"The promise (not to reveal to the media any information on the questioning plan) has been broken (by the probe team)," a presidential aide told Yonhap News Agency, declining to be identified.

"We are now very frustrated, with some arguing that we have to declare that we will no longer engage in any dialogue with the special counsel," he added.

Another aide to Park said, "If the independent counsel continues to leak content related to the questioning of the president, all mutual agreement reached will be rendered null and void."

Later in the day, the probe team confirmed that the questioning will not take place Thursday, saying it will reveal further details during a regular press briefing scheduled on the day.

An aide to Park said the questioning is likely to take place next week at the earliest, while denying speculation that the president is trying to avoid the interrogation.

Special prosecutors have been accelerating their probe into the high-profile corruption scandal involving the president and her longtime friend Choi Soon-sil, with their initial investigation period set to expire on Feb. 28. The period can be extended once, by a month, with consent from Acting President and Prime Minister Hwang Kyo-ahn.

Park is alleged to have colluded with Choi in extorting money and favors from local conglomerates. She is also suspected of allowing Choi to meddle in important state affairs including high-level government appointments. Both have flatly denied all charges made.

On the same day, the investigation team raided the home of Kim Hack-hyun, former vice chairman of the Fair Trade Commission, and questioned him over the controversial merger of Samsung Group's two affiliates in 2015. 

The country's largest business group is suspected of giving bribes to Choi in return for the state-run pension fund's backing of the merger between Samsung C&T Corp. and Cheil Industries Inc.

Investigators suspect that the presidential office also pressured the FTC to give favors to the conglomerate in the process. (Yonhap)