Which side is telling the truth, the ruling Saenuri Party or the main opposition Democratic United Party?

The two parties are confronting each other over the allegations that former President Roh Moo-hyun made remarks gravely detrimental to national interests during his summit with Kim Jong-il on Oct. 3, 2007.

The allegations were put forward by Chung Moon-hun, a Saenuri lawmaker who worked at Cheong Wa Dae as presidential secretary for unification affairs between 2009 and 2010.

During a parliamentary session on Monday, he alleged that Roh had pledged to nullify the Northern Limit Line during the summit in Pyongyang.

The NLL is the de facto border in the West Sea between the two Koreas. As such, if Chung’s allegation proves true, it means Roh promised to give up the South’s sovereignty over part of its maritime territory.

According to Chung, Roh also told Kim that he had willingly acted as a spokesperson for the North regarding its possession of nuclear weapons.

The lawmaker held a press conference Thursday to make additional revelations. According to him, Roh also pledged to pull out all U.S. troops from the capital area, which encompasses Seoul and its surrounding Gyeonggi Province.

Chung made the explosive allegations based on what he claimed to be the minutes of a closed-door conversation that Roh and Kim had during their summit.

The allegations were obviously directed at Moon Jae-in, the DUP presidential candidate who was chief of staff to the late president at the time of the summit.

Following Chung’s revelations, the ruling party mounted an offensive against Moon and the opposition party, calling for a joint parliamentary investigation to establish the truth.

Saenuri’s attack was in fact triggered by Moon himself. He said last week that should he win the presidential election, he would start talks immediately with the North to create a common fishing ground straddling the NLL.

Moon’s plan was reminiscent of a proposal that Roh made to the North during the summit. Yet Moon said his scheme would not involve altering the NLL.

In the face of the ruling party’s offensive, the DUP vehemently denied the existence of the minutes. The party’s leaders asserted that such a document could not exist because there was no private meeting between Roh and Kim during the summit in the first place.

Calling Chung’s allegations groundless, they denounced the ruling party for attempting to stage a mudslinging campaign against Moon.

Despite the DUP’s denials, it appears the document does exist. The minutes, if they really exist as claimed by Chung, must be a top-secret document whose perusal is strictly controlled. But Chung’s detailed allegations suggest he has perused it during his stint at Cheong Wa Dae.

So it may not be difficult to prove the existence of the document. Yet proving its existence is one thing, while disclosing it is another. Under the relevant law, disclosure of presidential records requires approval by two thirds or more of the National Assembly.

This means the document will be kept secret if the DUP lawmakers all oppose its disclosure. If the ruling party unilaterally discloses it, it would constitute a violation of the law.

It is against this backdrop that DUP’s floor leader Park Jie-won said he would accept the Saenuri Paty’s call for a joint parliamentary investigation should the document be disclosed confirming that Roh had made the alleged remarks.

Yet the opposition party should cooperate with the ruling party in investigating the allegations, especially the one regarding the NLL, as the cat is already out of the bag. If Roh had pledged to nullify the NLL, it would constitute a significant impairment to national interests. Such behavior should not be tolerated.

More importantly, the government and lawmakers should make it clear that the NLL is the maritime border between the two Koreas. Otherwise, it would cause unnecessary confusion among people in the South and lead the North to a serious misjudgment.