U.S. Rep. Chaka Fattah responded to charges against him Monday in a letter to the House of Representatives accusing the federal prosecutor on the case of bias and questioning the legality of the charges.

"For decades, appropriators in both the House and Senate have been the target of unconstitutional and illegal investigations," wrote Fattah, who was hit with a racketeering indictment two weeks ago, in the letter issued and published online this morning.

Fattah is a member of the House Committee on Appropriations, and recused himself from duties while charges are pending and he says in the letter he will face the charges at trial.

But in the letter to Reps. Jason Chaffetz and Elijah Cummings of the Committee on Oversight and Government Reform, Fattah urges them to require federal prosecutors to preserve every document related to his case for review and accused lead prosecutor Paul Gray of bias in the case.

Related: Fattah's son Chaka Fattah Jr. is representing himself in another federal indictment.

"He indicated that he knew for certain that Congressman Fattah was 'guilty of something.'"

Fattah also claims prosecutors investigating him violated the rights of citizens and congressional staffers by interviewing them at their homes and without attorneys present and presented false statements about him in court.

Related: Fattah says in interview that he is "provably innocent."

Fattah's defense attorney Kevin Mincey declined to comment on the case.

A spokeswoman for the U.S. Attorney's Office for the Eastern District had no comment on the Fattah's letter.

Just last week, Fattah tweeted pictures from a 2012 meeting of the National Fattah Conference on Higher Education, claiming that they contradicted claims in the federal indictment that Fattah obtained grants for a conference which never happened (see below).

However, Fattah's tweets refer to a conference in February, and the indictment states that a planned conference in October did not materialize.