Former Senate staffer Michael Brodkorb on Wednesday took the next step toward suing the Senate over his firing late last year in the wake of his affair with then-Senate Majority Leader Amy Koch.

Brodkorb, who was fired the day after Koch stepped down from leadership, filed a complaint with the federal Equal Employment Opportunity Commission (EEOC), claiming gender discrimination was at the root of his December termination.

Many steps remain before Brodkorb could actually sue the Senate, but he made it clear that he is prepared to take his former employer to court if necessary.

Breaking his three-month public silence on the issue, Brodkorb, known as a bruiser in Republican politics, said he wished he could have settled the issue quietly.

"I know the wheels of state government move slowly, but my attorneys and myself have made every attempt to work in a productive way with the Senate to mediate this issue out," Brodkorb said. He repeated twice more that he was "disappointed" and then renewed his public silence.

Dayle Nolan, the attorney the Senate hired to deal with the matter, said last week that there had been no negotiations toward mediation. Nolan and Senate officials did not return requests for comment on Brodkorb's filing.

The filing keeps the spotlight on a period that Republican lawmakers have said they would like to put behind them. The Senate on Friday will be confronted with another reminder -- an ethics committee will consider a complaint over how Sen. Geoff Michel, R-Edina, former deputy majority leader, handled the issue.

Senate officials have said the Brodkorb suit and the ethics complaint are baseless. Brodkorb was an "at will" employee who knew he could be fired at any time.

Brodkorb, who has said he deserves damages in excess of $500,000, alleges that he was treated differently than female employees who had similar affairs with legislators. To prove that, his attorneys have threatened to depose any current or former lawmaker and any staffers with whom they had affairs.

Brodkorb attorney Gregory Walsh said such depositions are simply part of the proof that would be offered in any employment lawsuit. Brodkorb's attorneys have said those depositions would be taken in private but the threat has still set Capitol tongues wagging about who could be called in.

Nolan, the Senate's attorney, said last week that she would try to block those interviews "as part of a fishing expedition by Mr. Brodkorb's attorneys."

David Allen Larson, professor of labor and employment law at Hamline University School of Law in St. Paul, said Brodkorb may have an "uphill battle."

The only way for Brodkorb to prove his case is to find an identical situation -- a female staffer who carried on an affair with a high-ranking member of the leadership -- that was handled differently from his own, Larson said. He will further have to prove that he lost his job just because he is a man, not because his bosses didn't like him, didn't approve of his job performance or thought he exercised poor judgment in his relations with the married Senate majority leader.

"The burden of persuasion will be on him," Larson said. "Whenever a man brings a sexual discrimination claim, it always raises eyebrows."

Meanwhile Wednesday, Brodkorb added a new possible angle for his legal efforts. His attorney, Phillip Vallaume, said Brodkorb is considering adding a defamation suit against Secretary of the Senate Cal Ludeman.

Last week, Ludeman suggested Brodkorb and his attorneys were seeking to extort and blackmail the Senate into settling.

Staff writer Jennifer Brooks contributed to this report. Rachel E. Stassen-Berger Twitter: @rachelsb