"It is shocking that US intelligence has been bugging allies, including South Korea. In particular, National Security Adviser Kim Sung-han and Presidential Secretary for Foreign Affairs Yi Mun-hui, who have reportedly been wiretapped, oversaw security and foreign relations decisions," Kwon Chil-seung, a former cabinet minister and currently a spokesperson for the main opposition Democratic Party, said.
Kwon noted that if media reports are true, the US actions are a violation of South Korea’s sovereignty and "seriously undermine trust" between the two countries.
Meanwhile, Democratic Party leader Lee Jae-myung criticized the presidential office for a possible security gap.
"While it is absurd in itself that a country's presidential office has been infiltrated for eavesdropping, it is also difficult to accept the fact of eavesdropping on the presidential office of an allied country in terms of common sense," Lee said.
Leader of the party's parliamentary faction, Park Hong-keun, suggested that the recent series of reshuffles in the country's diplomatic ranks is connected to US wiretapping.
Another democratic lawmaker, Kim Byung-joo, said that this situation cannot be resolved by discussions and it is "necessary to express a strong protest, demand clarification and punishment of those responsible."
The developments come ahead of South Korean President Yoon Suk-yeol’s meeting with US President Joe Biden on April 26.
US media reported last week that a new trove of classified documents leaked online revealed that US intelligence services spied on conversations at the South Korean presidential office regarding arms supply to Ukraine in early March. The South Korean presidential office said on Monday that it would seek "appropriate measures" from the US regarding this matter.