Attorney General Merrick B. Garland, facing a contempt vote in Congress, will lash out at House Republicans on Tuesday, accusing his critics of seeking to undermine the rule of law, peddling “conspiracy theories” and spreading falsehoods, according to his prepared remarks.

The usually mild-mannered Mr. Garland is expected to push back against the false accusation that the Justice Department was somehow behind the prosecution and subsequent conviction of former President Donald J. Trump on state charges.

“That conspiracy theory is an attack on the judicial process itself,” he is expected to say in testimony he will deliver to the House Judiciary Committee.

The committee and the House Oversight Committee recommended last month holding Mr. Garland in contempt for refusing to turn over audio recordings of interviews that Robert K. Hur, the special counsel, did with President Biden last year. Mr. Hur ultimately cleared Mr. Biden of criminal wrongdoing over his retention of classified material, despite faulting his memory and handling of sensitive documents. By contrast, prosecutors accused Mr. Trump of risking national security secrets by hoarding government records at his Mar-a-Lago resort.

“Certain members of this committee and the Oversight Committee are seeking contempt as a means of obtaining — for no legitimate purpose — sensitive law enforcement information that could harm the integrity of future investigations,” Mr. Garland is expected to say. He has argued that the recordings could be altered and used in pro-Trump political ads.

“I will not be intimidated,” his prepared remarks continue. “And the Justice Department will not be intimidated.

Last month, President Biden asserted executive privilege to deny House Republicans access to the recordings, denouncing their effort as a political stunt with dire implications for federal law enforcement.

It came two months after a transcript was made public.

The move was intended to shield the department, and Mr. Garland, from prosecution if House Republicans voted to hold him in contempt. They have yet to schedule a floor vote.

Mr. Garland said at the time that the bid by Republicans was the latest in “a series of unprecedented and, frankly, unfounded attacks” on the department and the rule of law.

On Tuesday, Mr. Garland is expected to tell Republicans that those efforts are feeding “heinous” threats against “individual career agents” and prosecutors.

“These attacks have not, and they will not, influence our decision making,” he is expected to say.