Federal prosecutors on Thursday asked the judge in the case against former New York City Police Commissioner Bernard Kerik to consider disqualifying Kerik's lawyer, saying he has a potential conflict of interest because he could be called as a witness.

Kerik, once President Bush's pick to lead the Department of Homeland Security, made admissions to the attorney, Kenneth Breen, that constituted obstruction of justice and were therefore not covered by attorney-client privilege, prosecutors said.

In a 12-page letter to Judge Stephen Robinson, U.S. Attorney Michael Garcia specified that there was no claim that Breen acted unethically or improperly, "only that the defendant did." He asked the judge to appoint a new lawyer who would advise Kerik about Breen's potential conflicts of interest and to consider disqualifying Breen.

Breen would not comment except to say, "We will address this motion in court."

Breen appeared with Kerik when he was indicted this month on 16 wide-ranging counts including accusations of lying to the White House, filing false income taxes, tampering with witnesses and avoiding the nanny tax.

Last year Kerik pleaded guilty to a misdemeanor charge in state court, admitting that renovations to his Bronx apartment constituted an illegal gift from the construction firm. The renovations are an issue in the federal indictment, as well.

Garcia said prosecutors intend to call a former Kerik attorney, Joseph Tacopina, as a witness to testify about what Garcia said were false claims to the Bronx district attorney's office. He said Kerik "personally obstructed that investigation by causing patently false statements to be made" to the district attorney's office about the renovations.

Besides questioning Tacopina, the letter says, "the Government may subpoena Breen for these purposes, in which case he would be an actual witness. But even in the absence of such a subpoena, he would be an unsworn witness ... to facts that go to the heart of many of the charges in the indictment."

On another matter — a reportedly false loan application — "the defendant's admissions to Tacopina and Breen are tantamount to a confession," the letter says.

"Given that Breen was the primary attorney in the prior investigation ... his defense of his client's conduct in that investigation will necessarily implicate his own credibility and be fraught with ethical issues," Garcia said.

Republican presidential candidate Rudy Giuliani appointed Kerik police commissioner in 2000 when he was New York mayor, and he endorsed Kerik's 2004 nomination to head the Department of Homeland Security. Days after President Bush introduced Kerik as his nominee, however, Kerik announced he was withdrawing his name because of tax issues involving his former nanny.

Giuliani has said he should have done a better job of vetting Kerik before backing him for the Homeland Security job.