The Democratic Party of Korea lawmakers on Thursday slammed the National Intelligence Service for declining to comment on the leak of classified US documents detailing an internal conversation between top South Korean officials.

The party's lawmakers used their majority to convene a plenary session on the Assembly’s intelligence committee unilaterally and accused the NIS of failing to provide an adequate explanation for the alleged US spying on the office of President Yoon Suk Yeol.

Rep. Youn Kun-young, the committee’s Democratic Party executive secretary, said that the NIS twice canceled without explanation appointments to brief him about what the intelligence service has learned about the spying allegations to date.

“The written response I got from the NIS is that there is no problem with wiretapping or other forms of surveillance of the presidential office,” he said. “This kind of response from our top intelligence agency makes no sense at all when the US has already practically admitted to spying on us.”

Youn added that, as the state agency chiefly responsible for the security of the presidential office, NIS officials should be summoned for questioning in the Assembly.

Another Democratic Party lawmaker on the committee, Rep. Lee Won-wook, said that his requests for clarification from the NIS have also been met by responses of "no comment."

“As Rep. Youn has said, the NIS said it was unable to give an explanation about the leak incident,” he said, adding that the intelligence service was “sowing public distrust” in the system.

The NIS declined to confirm the Democratic Party lawmakers’ claims.

Ruling Party Rep. Park Duk-hyum, heading the Assembly intelligence committee, said he hoped the ruling and opposition parties would reach an agreement on a plenary session as soon as possible.

The ruling People Power Party executive secretary of the intelligence committee, Rep. Yoo Sang-bum, said the opposition was “politicizing matters of national security” and pushing the Assembly through its majority to convene sessions without the agreement of both parties.