Promoter Main Events filed a lawsuit in U.S. District Court in New York on Wednesday against several parties, claiming they interfered with an agreement the company had in place to co-promote a light heavyweight unification fight between champion Adonis Stevenson and titleholder Sergey Kovalev in the fall.

Main Events, which promotes Kovalev, sued Stevenson, adviser Al Haymon (Stevenson's new representative), Stevenson promoter Yvon Michel, Groupe Yvon Michel (Michel's company), Golden Boy Promotions and Showtime, claiming breach of contract, tortious interference and fraud, among other accusations.

According to the suit, a copy of which was obtained by ESPN.com, Main Events is suing for unspecified damages and punitive damages against each party, although the company said it was seeking more than seven figures.

Light heavyweight champion Adonis Stevenson is one of several parties being sued by Main Events. AP Photo/The Canadian Press, Jacques Boissinot

"Main Events does not file lawsuits lightly," Main Events attorney Pat English told ESPN.com. "We are dead serious about pursuing the allegations of the complaint and anticipate that there will be a positive result both for Main Events and the sport of boxing."

Main Events chief executive Kathy Duva has long maintained that she and Michel made a deal for the fight on Jan. 23, agreeing in a series of emails, which she made public weeks ago and are in the filing. According to the suit, Duva and Michel on Jan. 24 agreed to a $2.4 million license fee for the fight on a conference call with HBO Sports executive Peter Nelson.

Stevenson-Kovalev, which would match the top two 175-pounders in the world, as well as tremendous, crowd-pleasing punchers in one of the most attractive fights in boxing, was to take place in the fall following each fighter's tune-up fight. Kovalev (24-0-1, 22 KOs) knocked out Cedric Agnew on March 29 and Stevenson (23-1, 20 KOs) is scheduled to face Andrezj Fonfara on May 24.

However, not long after Duva and Michel appeared to agree on every point for the bout, Stevenson signed an advisory deal with Haymon. Although assured that it would not have an impact on the Kovalev fight, the Stevenson camp soon sought to renegotiate its agreement with HBO for the Fonfara fight while at the same time shopping the bout to rival Showtime, which made an offer far greater than HBO's. HBO had the right to match but declined, and now Stevenson-Fonfara is scheduled to take place on Showtime with Stevenson and the network looking ahead to matching the boxer with light heavyweight titlist Bernard Hopkins, who is promoted by Golden Boy.

The lawsuit contends that Michel reneged on the deal and that Haymon interfered with the agreement, conspiring with Golden Boy and Showtime to instead match Stevenson with Hopkins in the fall.

"I have no idea why Golden Boy would even be involved," Golden Boy chief executive Richard Schaefer, in Las Vegas promoting Saturday night's Floyd Mayweather Jr.-Marcos Maidana Showtime PPV event, told ESPN.com. "We haven't seen the suit but I'm not going to worry about it. I'll let our attorneys handle it. But do we have an interest in Stevenson-Hopkins? Of course. If we can make that fight, we would love to make that fight."

The suit said that Main Events had no issue with Haymon trying to negotiate a better deal for Stevenson-Fonfara with Showtime, but that even if it did, Stevenson was still bound to the Kovalev fight on HBO in the fall.

"I think that our complaint quite clearly speaks for itself," Duva told ESPN.com. "Back in January we made a unification fight that everyone wanted to see. It was the fight that Sergey Kovalev asked for to test his skills against the best. Then some big players with their own agenda came along and interfered with my agreement. There are rules and they broke them. And it is my job to call them out on it. One of the reasons that we have a court system is to allow smaller players, like me, to protect themselves against the big boys when it becomes necessary."

In an even more serious charge, Duva contends that Haymon, who does not speak to the media or even like to be seen in public, is not just an adviser and manager but also acts as a promoter, which would be a violation of the federal Muhammad Ali Boxing Reform Act. The law makes it illegal in the United States to act as a manager (who has a fiduciary duty to the boxer) and a promoter (who doesn't have a fiduciary duty to the boxer).

The suit claims Haymon "has a relationship with Showtime wherein certain promoters rely upon Mr. Haymon for allocation of television dates and rights fees rather than negotiating those dates and fees directly with Showtime. Haymon has entered into an alliance with Richard Schaefer. ... One object of this alliance is to wrest control of Golden Boy from Oscar De La Hoya for their own financial gain."

Schaefer and De La Hoya have been at odds for months and it is widely believed that Schaefer could soon be leaving Golden Boy to work with Haymon.

The lawsuit accuses Schaefer of breaking his fiduciary duty to Golden Boy by not requiring promotional contracts with Haymon fighters and instead simply relying on Haymon's "good will, placing the corporation in a weakened position." The suit also accuses Showtime Sports chief Stephen Espinoza of knowingly having "the clear intent of disrupting the Stevenson-Kovalev bout."

"We haven't seen a copy of the lawsuit so it would be irresponsible to comment on without having reviewed it or discussed it with legal," Espinoza told ESPN.com.

Michel did not respond to a request for comment.