Park arrived in the United States this week for her first official visit, which included a meeting with U.S. President Barack Obama, delivering a speech at a joint session of the U.S. Congress and leading a large business delegation that included Samsung Chairman Lee Kun-hee and Hyundai Motor Chairman Chung Mong-koo, Yonhap news agency reported.
Park's otherwise successful trip was damaged by sexual assault allegations made against her spokesman, Yoon Chang-jung, who was accused of assaulting a Korean-American woman Tuesday at a hotel in Washington.
District of Columbia police said they are "investigating the report of a misdemeanor sexual abuse" by a 56-year-old male suspect. A police report said the suspect "grabbed her buttocks without her permission."
The report didn't identify the suspect but the age matches that of Yoon, who returned to Seoul Wednesday and was questioned by the office of the senior presidential secretary for civil affairs, presidential officials said.
"[Yoon] completely poured cold water over the accomplishments of the U.S. visit," one presidential official, speaking on condition of anonymity, told Yonhap. "It's causing an extreme burden to state affairs."
South Korean main opposition Democratic Party called the scandal a "foreseeable tragedy" and has, along with the ruling Saenuri Party, called for an investigation into the incident, as well as a public apology.
"President Park and Cheong Wa Dae should deeply reflect on the drop in national status brought about by the wrong appointment of personnel and apologize to the people," DP spokeswoman Rep. Bae Jae-jeung said in a news briefing. Cheong Wa Dae is the name of South Korea's presidential office.
"If the allegations of sexual assault are true, it is something that cannot and should not happen," said Saenuri spokeswoman Rep. Min Hyun-joo. "Not a single speck of doubt must be left with the public through a thorough investigation of the facts and the truth."
Park, who took office in February, was to return to South Korea Friday.