Government lawyers asked yesterday that a Washington lawyer be disqualified from representing 15 Libyans who are targets of an investigation by a federal grand jury in Alexandria because he has a conflict of interest.

The grand jury is looking into allegations that supporters of Libyan leader Col. Muammar Qaddafi plotted to assassinate at least three anti-Qaddafi Libyans in the United States, according to sources familiar with the investigation.

Justice Department lawyer Karen Ane Morrissette told U.S. District Court Judge Albert V. Bryan Jr. in Alexandria federal court that lawyer Richard C. Shadyac "should be disqualified from representation of these individuals and we intend to file such a motion." Morrissette also told Bryan that Shadyac's clients were targets in the federal investigation.

Shadyac, who does legal work for the Libyan government in the United States, confirmed that he received a letter from the Justice Department Wednesday challenging his representation of the 15 Libyans who were named as targets of the probe. He declined to specify the government's objections, but said "they're getting awfully personal."

A Justice Department spokesman refused to elaborate on the reasons for the department's position.

In a related action yesterday, Bryan ordered the government to return the passports that it seized last week from Shadyac's Libyan clients when they answered subpoenas to appear before the grand jury. Bryan said the government could keep copies of the passports and the Libyans would not be allowed to contest the authenticity of those copies in any future legal proceeding.

Morrissette argued against returning the passports, saying they are relevant to the federal investigation. She said they provided evidence about the Libyans' travel and that "the government has reason to believe there may have been a misuse of the passports."

Shadyac's clients, whom he described as students in this country, refused to testify before the federal grand jury last week, pleading their constitutional right against self-incrimination. Five of them were given immunity from prosecution and ordered to answer questions.

The Justice Department is looking into whether any of the five committed perjury during their testimony, a source close to the investigation said. This is standard practice in investigations of this kind, the source said.

On Tuesday, the State Department expelled Farhat Tibar, a Libyan diplomat working at the country's United Nations mission, after the FBI told the department that Tibar was suspected of being linked to the alleged assassination plot.