Federal prosecutors on Tuesday challenged former national security adviser Michael Flynn’s claim that the U.S. Justice Department has withheld exculpatory evidence from him, arguing that his defense lawyers were advancing unfounded “conspiracy theories” in the hope of upending his guilty plea.

In a 22-page court filing, prosecutors urged a federal judge in Washing to reject Flynn’s request for evidence he believes was improperly hidden from him, saying the demand from his new defense lawyers amounted to a “fishing expedition.” Prosecutors also pointed to statements Flynn made last year in which he denied having any concerns about whether the Justice Department had met its obligation to turn over potentially exculpatory evidence, known as Brady material.