The escalating scandal surrounding the leak of a telephone conversation between President Moon Jae-in and US President Donald Trump earlier this month is yet another case that shows how extreme partisan confrontation damages national interests.

The core element of the case is that a diplomat stationed in Washington handed over the script of a telephone conversation between the two leaders to an opposition lawmaker with whom he has a close personal relationship.

The lawmaker, Rep. Khang Hyo-shang of the Liberty Korea Party, used the information to attack Moon for “begging” Trump to visit South Korea on his way home from a visit to Japan.

Both the diplomat, who now faces disciplinary action by the Ministry of Foreign Affairs, and Khang, under heavy political fire, must share responsibility. The diplomat especially deserves heavy punishment because he must have known that conversation between the president and a foreign leader was Class-3 classified information.

Khang cannot escape criticism that what he did amounts to spying on classified diplomatic information through his personal acquaintance. The two went to the same high school and university. The information Khang used in his news conference on the Moon-Trump telephone talk did not include highly sensitive information, but it nonetheless did not amount to an act of whistleblowing as his Liberty Korea Party alleges. It has little to do with the public’s right to know either.

Indeed, even some of Khang’s party colleagues and other conservative figures have lined up to rebuke the journalist-turned-lawmaker and diplomat, who was recalled Sunday for disciplinary action.

One harsh criticism came from Rep. Yoon Sang-hyun of the Liberty Korea Party who heads the National Assembly Foreign Affairs and Unification Committee. He wrote on Facebook that Khang damaged national interests for the sake of partisan interests.

Former UN Secretary-General Ban Ki-moon and Chun Young-woo, a former career diplomat who served as the top foreign policy and security aide to conservative former president Lee Myung-bak, also joined the fray.

Ban said that usually conversations between leaders should be kept confidential for as long as 30 years. “It should not have happened,” he said, adding that it is more unfortunate that such information was leaked to a politician.

Now Khang may have to face legal repercussions as the ruling Democratic Party has notified the state prosecutors, accusing him of leaking diplomatic secrets. It could set a new precedent on the limitations of lawmakers’ privilege of speech.

Meanwhile, the growing criticism against Khang should not free Cheong Wa Dae and the ruling party from some responsibilities of their own.

When Khang described Moon’s comments to Trump, at the news conference May 9, two days after the leaders had held the telephone conversation, Cheong Wa Dae denied key elements of his statement.

It is simply self-contradictory that the presidential office which had dismissed Khang’s statement as a lie now says that the lawmaker disclosed “national secrets” and that he should be punished.

One more question involving the ruling camp is the case of former ruling party lawmaker Jung Chung-rae, who claimed in January last year that he obtained “all the raw data” of a telephone conversation between Moon and Trump.

After the Khang scandal broke out, Jung changed his position and insisted that what he said in a television talk show at the time was based only on what the presidential spokesperson had made pubic previously.

It would only be fair that both Cheong Wa Dae and the Foreign Ministry investigate the case as vigorously as they did with the case of Khang and the diplomat. This is necessary because of the need to make sure that diplomatic information is not exploited again for domestic politics.