AceShowbiz - Bosses at DC Comics have stepped up their fight to retain control of "Superman". They have filed suit against the lawyer representing the heirs of the character's co-creators in a bid to scupper their copyright claim.

The estate of artist Joseph Shuster is battling to regain copyright of the comic strip character in 2013, when DC Comics and Warner Bros. are expected to lose control of the rights. Lawyer Marc Toberoff, who succeeded in returning part of the copyright to the heirs of writer Jerome Siegel in 2008 and 2009, is representing the Shuster clan - but he has been rocked by a lawsuit from DC Comics bosses alleging he is trying to profit from the case.

They claim Toberoff has an ulterior motive and wants to gain a share in the rights himself, and has also prevented his clients from entering into talks with DC Comics. But Toberoff has now hit back, filing a motion to have the "desperate and cynical" lawsuit dismissed, according to Variety.com.

In papers filed at the U.S. District Court in Los Angeles on Friday, August 13, his legal team states: "The transparent purpose of DC's lawsuit against Mr. Toberoff is to re-litigate the issues that DC has already lost, disrupt the relationship between Mr. Toberoff and his clients, and delay the final reckoning between DC and Mr. Toberoff's clients."