Donald E. Lukens' final days in Congress were spent out of public view, on the telephone with people urging him to resign rather than face a second sexual misconduct investigation.

He didn't appear at the House on Tuesday or Wednesday. He slipped out of his congressional office Monday, before the House ethics committee announced it had reopened his case because of a new complaint that he sexually harassed a Capitol elevator operator.Lukens' last official action was a letter of resignation transmitted to Ohio Gov. Richard Celeste shortly after 11:30 a.m. Wednesday:

"Effective immediately, for the good of the Congress and the integrity of the institution, I resign my seat in the U.S. House of Representatives. Sincerely, Buz."

A top aide said Lukens stayed away from Capitol Hill but kept in contact with supporters, staff, his attorney and party leaders via telephone.

House Republican Leader Robert Michel was among those who convinced Lukens, defeated for renomination in Ohio's May primary, that he faced an expulsion vote unless he stepped down.

Ethics committee spokeswoman Jan Keyes said Lukens would not have lost his retirement benefits even if he had been expelled.

Lukens will qualify for a pension of more than $2,000 a month beginning in 1993. Under the federal pension system, his payment is determined by combining his congressional service with his 6 1/2 years in the Air Force and two years on a congressional staff.

Lukens resigned two days after the ethics committee revived its dormant case against him to include the new accusation that he fondled a House elevator operator earlier this month.