Acting President Choi Sang-mok, center, speaks during a Cabinet meeting at the Government Complex Seoul, Friday. Yonhap

Acting President Choi Sang-mok exercised his second veto on the opposition-led special counsel bill aimed at investigating President Yoon Suk Yeol over charges of insurrection, Friday.

He cited "unconstitutional" provisions in the bill and the need to protect secrets related to national security.

During a Cabinet meeting at the Government Complex Seoul, Choi said that while the bill had addressed some of the unconstitutional elements in the version he vetoed on Dec. 31, it was still passed unilaterally by the opposition without the bipartisan agreement that he had previously requested.

"The bill still contains unconstitutional elements and poses potential risks of leaking security secrets," he said.

Choi emphasized that the introduction of a special counsel should be approached with caution.

"As a special counsel is an exceptional measure, outside the principle of separation of powers, it should only be used in limited cases where the fairness and objectivity of an investigation are in doubt," he said, explaining that many have voiced that there is no need for a separate special counsel probe right now because the prosecution's investigation into the martial law case is already progressing.

"The prosecution's investigation into the case is ongoing, and key figures, including the sitting president, have been detained and indicted, and court proceedings are underway. Given these, it is difficult to see the need for introducing a special counsel at this point," Choi said.

He also highlighted that the international community is closely watching Korea's normalization and recovery processes.

"In this context, I believe that, rather than establishing a new investigative body, it is more important to ensure the fair and transparent determination of the facts through the ongoing judicial proceedings."

The main opposition Democratic Party of Korea (DPK) first passed a special counsel bill on Dec. 12 to dig into Yoon's insurrection charges related to the martial law declaration. That bill was vetoed on Dec. 31 and dismissed during the National Assembly's revote. In response, the DPK revised parts of the bill and reintroduced it on Jan. 17 after negotiations fell through with the ruling People Power Party (PPP).

The modified bill excluded Yoon's treason charges from the scope of the investigation but continued to target allegations related to the Dec. 3 martial law declaration, including attempts by the president and others to seize control of the National Assembly and the National Election Commission, as well as attempts to arrest and detain certain politicians, civil servants and citizens.

Arguing that the bill still contains unconstitutional elements, the PPP requested that the acting president exercise his veto power.

With Choi's veto, the government will send the bill back to the Assembly for a revote. The bill can become law if a majority of lawmakers are present and at least two-thirds of those present vote in favor. Otherwise, it will be scrapped.

This marks the seventh time Choi has exercised his veto right since assuming the acting presidency, following the Assembly's passage of a bill to impeach Prime Minister Han Duck-soo on Dec. 27. Besides the two special counsel bills, Choi has vetoed five other bills, including one related to an investigation into allegations surrounding first lady Kim Keon Hee.