Prosecutor General Lee One-seok on Monday apologized for the prosecution's secretive questioning of first lady Kim Keon Hee over the weekend, saying that investigation principles were neglected while interrogating her.

The Seoul Central District Prosecutors' Office questioned Kim as a suspect at an undisclosed venue believed to be somewhere other than a prosecutors' office. The prosecution general, whose Supreme Prosecutors Office oversees the Seoul office, said he was not briefed about the case until hours into the interrogation, and that he was not aware of questioning taking place somewhere outside of a prosecution office until then.

Traditionally, high-profile suspects have stood in front of cameras before they enter a prosecutor's office to face interrogations, although there were efforts by the previous administration to end the practice.

Lee's revelation Monday puts the South Korean prosecution in disarray as the questioning of the first lady was carried out without the top prosecutor's approval.

Under the law, the prosecutor general is authorized to "direct and supervise" officials in any of the prosecutors' offices.

The ruling party, however, backed the decision by Seoul district prosecutors' office that questioning the first lady in an outside venue was "appropriate" in considerations of safety.

Kim, the wife of President Yoon Suk Yeol who was inaugurated in May 2022, has been facing multiple allegations, including involvement in illegal stock price manipulation in the early 2000s and an antigraft law violation for her acceptance of a 3 million won ($2,160) Dior bag in September 2022 that was recorded by a spy camera and later released online.

"I have repeatedly promised many times to people that there will be no place for exception or immunity from criminal prosecution," Lee told reporters on the way to his office in Seoul.

"But such a principle was simply neglected in our investigation into the president's wife, so I could not keep the promise I've made with the people."

Lee's remarks came in an apologetic tone, after he promised in May to "swiftly and sternly investigate (Kim) based on evidence and according to law and principle." The prosecution launched the probe into Kim's alleged antigraft violation, five months after a criminal complaint was filed against her.

Now two months on, Lee said, "I could not get any notification from a district-level prosecutors' office," in an apparent reference to Lee Chang-soo, chief of the Seoul Central District Prosecutors' Office, who had failed to either notify or consult with him about the procedures of the probe into South Korea's first lady.

"But I feel responsible for not being able to lead the prosecutors there in the right way. I deeply apologize for what I'm liable for," said Lee One-seok.

The prosecutor general added he would take proper measures against Lee Chang-soo, who reportedly expressed regret that he could not inform his senior of the investigation. Lee Chang-soo, who was a spokesperson for Yoon when the president was the nation's top prosecutor, reportedly said that his decision stemmed from the concern that the prosecutor general may oppose the plan to question Kim outside the prosecutors' offices.

"I'll put my utmost effort to restore the principle of judicial impartiality as stipulated in the Constitution," the prosecutor general said, whose two years of service is to end in September.

The prosecutor general made his remarks after the Seoul Central District Prosecutors' Office said that it had conducted a prosecutorial interrogation Saturday against Kim at an unidentified venue, which it called "a government agency (related to) security under its control." The venue is reportedly believed to be an office of the Presidential Security Service outside the presidential office in Yongsan-gu, Seoul.

Some within the ruling bloc, however, hit back at Lee One-seok's claims. Rep. Jeong Jeom-sig, policy chief of the People Power Party, also pointed to the past experience of Rep. Choo Mi-ae, a former justice minister, depriving Yoon, the then top prosecutor, of his power to supervise a public prosecutor.

The main opposition Democratic Party of Korea and other parties have joined forces to denounce the presidential office.

The Democratic Party's acting chair Rep. Park Chan-dae, said in a meeting Monday at the National Assembly that the way Saturday's questioning of the first lady was carried out showed that the prosecution had surrendered itself to the presidential office and has no intention of bringing a powerful figure to justice, doubling down on the party's claims that the first lady must undergo a special counsel probe.

Her Eun-a, a former lawmaker who now leads the opposition New Reform Party, said the fact that Kim is the first lady of South Korea does not mean she "deserves special treatment" in the face of criminal prosecution.

Rep. Cho Kuk of the Rebuilding Korea Party described Kim as "a Korean version of Empress Wu Zeitan" known for her despotic ruling of China in the 7th century.

No first lady in South Korea was interrogated while her husband was in office. The wives of late former presidents Chun Doo-hwan, and Roh Moo-hyun, as well as former president Lee Myung-bak underwent questioning, but these interrogations took place after their service as the first lady ended.

An official of the presidential office on Monday said on condition of anonymity that the criticism that first lady Kim had received preferential treatment is an overstatement given that the prosecution's questioning of a South Korean first lady was unprecedented. The official declined to comment further, citing the fact that the investigation into Kim is ongoing.