Washington (CNN) President Donald Trump's first national security adviser Michael Flynn should serve up to six months in jail, prosecutors told a federal judge on Tuesday, saying Flynn has failed to accept responsibility for his actions and undermined a separate criminal case.

The sentencing memo shows just how harshly the Justice Department responds to Flynn's recent attempts to unravel his guilty plea in the Mueller investigation and says that he sought to thwart the government's investigation into his former business partner, an abrupt turn from Flynn's months of cooperation and public reticence during the special counsel's probe.

"It is clear that the defendant has not learned his lesson," the Justice Department wrote. "He has behaved as though the law does not apply to him, and as if there are no consequences for his actions."

Flynn, 61, is set to be sentenced on January 28, more than two years since he pleaded guilty to lying to federal investigators.

"Given the serious nature of the defendant's offense, his apparent failure to accept responsibility, his failure to complete his cooperation in -- and his affirmative efforts to undermine -- the prosecution of Bijan Rafiekian (also known as Bijan Kian) and the need to promote respect for the law and adequately deter such criminal conduct," prosecutors wrote, recommending between zero and six months in jail.

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