St. Elizabeths Hospital officials said they placed Dr. Walter M. Presnell on paid leave at his request yesterday, as administrators stepped up an investigation of alleged sexual abuse of a male patient by Presnell in the 1970s in a Boston suburb.

Presnell was relieved of patient-care duties at the hospital last week, also at his request, following inquiries by The Post about the allegations and his training and employment history, according to hospital spokesman Harold Thomas.

Thomas has said hospital officials were unaware of the allegations during the six years Presnell has worked as a $64,764-a-year staff psychiatrist at the federally owned facility in Southeast Washington.

Thomas said yesterday that he did not know how long Presnell would remain on leave. Presnell, reached at his home in Northwest, declined to comment.

The allegations, which Presnell denies, were contained in a lawsuit filed by the former patient in U.S. District Court in Boston and settled in early April for $225,000 by Presnell's malpractice insurance carriers.

According to sworn depositions given in connection with the complaint, Presnell, 59, allegedly was terminated or allowed to resign on five occasions from training or staff positions during his career before being hired by St. Elizabeths.

A spokeswoman for the U.S. Department of Health and Human Services, the hospital's parent agency, said yesterday that officials are investigating a complaint filed in January by Daniel Burnstein, the patient's lawyer, but declined to comment further.

Thomas said St. Elizabeths will "explore every option the personnel system allows us . . . . Various supervisors now would like to discuss the allegations with Dr. Presnell."

Thomas said a task force of hospital personnel officials, formed last week, will "use this as a case study to see what went wrong."

Physicians seeking jobs at St. Elizabeths must complete standard application forms, including a five-year history of training and employment, and provide a list of three references who normally are contacted by the hospital by letter, according to Thomas.

Asked if St. Elizabeths relies heavily on information supplied by the applicant about credentials, Thomas said: "Yes, oh yes, like any federal agency . . . . We do not have investigators. Part of the thing is faith; we rely on applicants being truthful, under penalty of law."