The leaders of the planned new opposition party on Sunday called for a special investigation into alleged evidence fabrication by the National Intelligence Service, raising pressure on President Park Geun-hye over the issue.

Saying that the spy agency was “threatening the foundations of democracy,” Reps. Kim Han-gil and Ahn Cheol-soo ― the co-chiefs of the party launch committee ― said that the president should end her silence on the issue.

“The president should take stern measures to prevent the repeat of such situations that shake the foundations of the country by uncovering the truth and punishing those responsible,” Kim and Ahn said in a joint press conference. 

They added that related developments were destabilizing the foundations of the country’s legal system, and damaging national security and diplomatic relations.

“If the prosecution’s investigation is insufficient, the government should appoint a special counsel to leave no doubt.”

The case, which began last year, revolves around a former Seoul Metropolitan Government official accused spying for North Korea.

Although the defendant, Yoo Woo-seong, a North Korean of Chinese descent who came to the South in 2004, was initially acquitted, the prosecution appealed with new Chinese documents allegedly proving that Yoo had traveled to North Korea as late as 2006.

The prosecution said the documents were provided by the NIS, which secured them through one of its agents working at the South Korean mission in Shenyang, China.

The authenticity of the evidence, however, came into question when the Chinese Embassy in Seoul claimed that they were not genuine Chinese government documents.

In addition, a Korean-Chinese NIS collaborator claimed that he forged the documents. The collaborator, identified as Kim, attempted suicide last week leaving a note claiming that the NIS owed him money for the forged documents.

Although Kim claimed that he forged documents for the NIS, he also wrote in his will that he was certain that Yoo was a North Korean spy.

Kim is also reported to have told the investigators that he had been working for the NIS, and that he was ordered to submit documents to disprove Yoo’s defense, for which he was given 7 million won ($6,570).

Following the allegations, the prosecutors’ office launched a verification team, which was upgraded to an investigation team Friday.

The investigators are reported to have issued travel bans on about five NIS agents linked to the case.

By Choi He-suk (cheesuk@heraldcorp.com)