Federal prosecutors tipped their hand yesterday in their corruption case against a former New York City police commissioner, saying they intended to call Bernard Kerik’s defense attorneys as witnesses in his upcoming trial. The trial strategy, which prosecutors disclosed in a court filing, is a costly setback for Mr. Kerik, as he may now need to find a new lawyer to represent him. Prosecutors say they intend to call Mr. Kerik’s current attorney, Kenneth Breen of Paul Hastings LLP, and a former lawyer, Joseph Tacopina, to testify that Mr. Kerik lied during earlier plea negotiations with the office of the Bronx district attorney.

Prosecutors are asking that Mr. Breen be taken off the case because of the conflict of interest in testifying against his client, according to the court filing, which is signed by assistant U.S. attorneys Perry Carbone and Elliott Jacobson.

Last year Mr. Kerik pleaded guilty to state misdemeanor charges for accepting renovations to his Riverdale apartment in 1999 and 2000 from a company seeking to do business with the city. Federal prosecutors say that Mr. Kerik, who was police commissioner between 2000 and 2001, told his two lawyers that he had paid for the renovations himself, which the lawyers in turn told Bronx prosecutors. Now federal prosecutors say they will ask Mr. Tacopina and possibly Mr. Breen to discuss what Mr. Tacopina told them to relay to the state prosecutors, the court filing said.

Mr. Tacopina withdrew from the case in April because of the conflict, a source close to him said. Mr. Breen could not be reached for comment yesterday afternoon.