Key members of an American human rights group that accompanied dissident leader Kim Dae Jung home from exile left today without an apology from the South Korean government for a scuffle with police on arrival last week.

Their departure came as South Koreans prepared to elect a National Assembly Tuesday, following a 20-day campaign in which opposition candidates have invoked Kim's name repeatedly.

The delegation cochairman, Rep. Edward F. Feighan (D-Ohio), met this morning with U.S. Ambassador Richard L. Walker to discuss the delegation's three days in Seoul. Walker and the group have traded numerous charges about each other's behavior. But an embassy spokesman said the meeting was cordial. Feighan left the country later in the day.

On Sunday, Feighan said he thought the group had accomplished its main goal in coming. "Our presence did add to Kim's safety and security," he said.

Other key delegation members, former assistant secretary of state for human rights Patt Derian and ex-ambassador to El Salvador Robert E. White, also departed. Rep. Thomas M. Foglietta (D-Pa.) stayed behind for a tour of U.S. military facilities in South Korea.

The group, charging that they were assaulted by security police at Kimpo International Airport on their arrival Friday, had pressed for an apology from the government.

Walker has lodged a written protest with the Foreign Ministry. An embassy spokesman said the government has affirmed that it is investigating the incident and will respond to Walker's note.

Government spokesmen have denied that brutality occurred and have blamed the incident on the refusal of Kim and the delegation members to follow police directions.

Kim spent another day confined to his house by police. Reached by telephone, he said he was waiting for a response from the government to a request he made yesterday to lift his house arrest on the ground that it was illegal.

Kim said he did not feel his situation was changed by the Americans' departure. "I must manage my problems by myself," he said, adding that he would await results of Tuesday's voting before deciding his next move. It has been predicted that 75 percent of the 24 million eligible voters will vote in the election of 276 National Assembly members.

The ruling Democratic Justice Party of President Chun Doo Hwan is expected to retain its majority.

Opposition parties are contesting the campaign energetically, despite their claims that a fair vote is impossible under the current election law and with 15 of their key leaders banned from taking part in politics.

The most dynamic of three opposition parties is the recently organized New Korea Democratic Party, which includes many followers of Kim Dae Jung and another opposition leader, Kim Young Sam.

In rallies around the country, its candidates have stressed their past links to Kim Dae Jung and accused the Chun government of being a "military dictatorship."

In a press conference this morning, representatives of the ruling party appealed for votes on the ground that they had brought stability and economic growth.

Opposition party representatives, in turn, called for direct election of the president, more democratic freedoms and changes in the press and labor laws.