Former Rep. Aaron Schock (R-IL), best known as the “Downton Abbey” congressman, is charging that federal investigators broke the law in using a staffer in his Peoria, Illinois office as an informant to bring a federal corruption case against him.

The former congressman’s lawyers alleged in a Tuesday court filing that FBI investigators had the staffer make secret recordings, in addition to stealing documents and receipts from Schock’s office.

Schock was indicted by a grand jury in November on 24 counts, including improperly using campaign and government funds and falsifying documents. He resigned from Congress in 2015 amid a swirl of questions about his lavish “Downton Abbey”-inspired office decor and jet-setting lifestyle.

But his lawyers may seek to dismiss the case by accusing federal investigators of turning Schock’s staffer into an informant and using that staffer to retrieve information the investigators could not obtain themselves.

The lawyers wrote that it’s unclear “the full extent to which the prosecutor and the investigating agents directed the CI to engage in illegal/or improper activities, and what use the government made of the ill-gotten fruits of the CI’s efforts.” But they argued that investigators may have exceeded their authority in the way they used the informant.

“The government, however, cannot run away from what was produced: a trail of improper — if not outright illegal — acts by the CI that remain not fully known to the defense in this case,” the lawyers wrote.