Former U.S. national security adviser Michael Flynn has dismissed the lawyers who represented him in his guilty plea and cooperation with special counsel Robert Mueller and retained new counsel, according to a court filing on Thursday.

While no reason was given for the termination of Robert Kelner and Stephen Anthony of the Covington & Burling law firm, the move comes after a contentious hearing in December when a judge excoriated Flynn for lying to the FBI and other actions leading to his guilty plea.

The judge's comments were prompted by a sentencing memo in which Kelner and Anthony noted that Flynn was not explicitly warned by FBI agents that lying to them was a crime, appearing to suggest that he was entrapped.