National Assembly Speaker Kim Jin-pyo criticized former Democratic Party of Korea colleagues who said the parliamentary leader does not need to maintain political neutrality.

In a radio interview late Sunday, Kim said that the Democratic Party “ought to be ashamed” of its criticisms that he was “not picking a side” as the party pushes for its post-Assembly election agenda.

“The speaker of the Assembly remains unaffiliated with any party for a reason. The speaker, who leads the legislature, must exercise his or her neutrality in keeping the executive branch in check,” he said.

He went on, “The ruling and opposition parties are supposed to find a middle ground through dialogue and compromise, but unfortunately both sides are proving themselves to be intransigent and confrontational instead.”

The attacks on Kim came from some of the biggest names in the Democratic Party, who are also vying to be the next speaker.

In a provocative radio interview, Park Jie-won, who was elected a fifth time as a lawmaker with the Democratic Party in the April general election, called the speaker a “real son of a b----” for not cooperating with the party’s timetable.

“We shouldn’t take him back when his speakership term is over,” said Park, who has suggested in previous interviews that he may run for speaker.

Another potential speaker candidate, Choo Mi-ae, who was justice minister for the last Democratic Party President Moon Jae-in, similarly said in postelection interviews that “the speaker of the Assembly does not need to stay neutral.”

The names being floated as candidates to be the next speaker so far are Democratic Party hardliners such as Park and Choo.

Last week, the Democratic Party slammed the speaker for going abroad for an interparliamentary meeting at a time when the party is pushing a special counsel investigation into the death of a Marine in July last year, on top of another led by the anti-corruption investigative agency.

The Corruption Investigation Office for High-Ranking Officials is investigating former defense chief Lee Jong-sup and others who served on or are still part of President Yoon Suk Yeol’s government over possible wrongdoing in the case.

Cpl. Chae Su-geun died while on a search and rescue mission to find people who had gone missing amid heavy rainfall that had hit the country.

Allegations surrounding his death became one of the key issues in the Assembly election in April, with the Democratic Party pledging to open a special counsel investigation.

Ahead of the trip, Democratic Party lawmakers threatened to “block the speaker from leaving the country” until he agreed to convene an Assembly session to put the special counsel bill to a vote -- a request which he complied.

Kim said the Democratic Party, of which he had long been a part until his election as speaker, was “abusing its majority and catering to its base” on the party’s calls for canceling his prescheduled trip.

The Assembly-controlling Democratic Party voted to pass the special counsel bill in a session convened Thursday without consent from the ruling People Power Party.

On Saturday, Kim left for the US for the 10th meeting of MIKTA -- a group of the five “middle-power” countries Mexico, Indonesia, South Korea, Turkey and Australia. He is also due to make stops in Brazil and Argentina.