Allegations that Prince William County prosecutor Paul B. Ebert received sexual favors in exchange for lenient treatment for a woman convicted of drug dealing were found "to be without merit," the U.S. attorney's office in Alexandria said yesterday.

A statement by the office also said that a three-month investigation "found insufficient evidence" of any federal violation by Ebert, a Democrat, who has been commonwealth's attorney for the county for 18 years.

"I'm extremely elated," Ebert, 48, said yesterday. "I knew from the onset there was no merit . . . . I'm sorry it received the publicity it did."

The office of Virginia Attorney General Mary Sue Terry has not made a decision about possible violations of state laws because it has not yet reviewed the results of a State Police investigation into the allegations, according to Stephen Rosenthal, deputy attorney general for the criminal division.

Terry authorized a separate State Police investigation after Ebert asked for it "to clear my name."

The investigations were initiated by allegations from June Kay Carter, 26, who told FBI investigators last April that Ebert had had sex with her twice, once in his courthouse office in Manassas last December and once at a motel in 1982.

She was interviewed by the FBI in the Prince William-Manassas Regional Adult Detention Center, where she was serving a sentence for violating probation for a 1982 drug conviction.

Carter said Ebert had recommended or approved her release from jail on personal recognizance and her participation in work-release programs despite her history of escape, failure to make court appearances and continuing drug abuse and prostitution. She also alleged that Ebert had fixed traffic tickets for her and said she had passed a lie-detector test given by the U.S. attorney's office in April.

Ebert vehemently denied the charges, calling them "a damned lie." He said he had known Carter since she was a teen-ager and had given her lenient treatment because he felt sorry for her or because she occasionally cooperated as an informant with local vice officers.

Ebert passed a lie-detector test early in the investigation, his attorney, Plato Cacheris, said yesterday. He was not called to testify before the Alexandria federal grand jury that heard evidence in the case.

Carter, who was released on parole from the Prince William-Manassas center last week, could not be reached for comment yesterday.

U.S. Attorney Henry E. Hudson, a Republican, said he issued yesterday's statement because in cases where an official is being investigated, "we have as much an obligation to announce he has been exonerated as we do to announce an indictment."

The outcomes of grand jury investigations are not usually disclosed except when there is an indictment.

Alexandria lawyer T. Brooke Howard, who represented Carter at Ebert's request at least twice, said yesterday he was "happy to hear the news" about the county prosecutor. "It could not happen to a better man. He's a fine, clean gentleman," Howard said.

Ebert suggested Carter's allegations were part of a trend. "It seems more prisoners are attacking the prosecution throughout the commonwealth these days and this office is no exception," he said yesterday.