NEW YORK, May 23 (Reuters) Wham-O has hit Goodwin Procter with a lawsuit that claims the law firm overbilled it by racking up $5 million in legal fees.

The lawsuit filed on Friday stems from Goodwin Procter's representation of Wham-O in trademark infringement litigation involving its Frisbee, Slip 'n Slide and Hula Hoop against other toy manufacturers.

The action, filed in California state court, alleged that Goodwin Procter's fees were "excessive, unreasonable and not necessary" for work billed from January 2009 to April 2010. Wham-O claimed breach of contract and asked for a declaratory judgment to determine what portion of Goodwin Procter's $5 million legal bill it owes.

In April, an arbitrator ruled that Wham-O owed Goodwin Procter $4.7 million, but the toymaker has rejected that ruling as nonbinding. In Friday's suit, Wham-O also asked the court for a finding regarding the enforceability of the arbitration clause in the parties' fee agreement.

"We're currently in settlement discussions with Wham-O," said Lee Feldman, a spokesman for Goodwin Procter. He said Friday's lawsuit was filed so that Wham-O could preserve its right to contest the arbitration award granted in April. Stephen Chazen, an attorney in Sherman Oaks, Calif., is representing Wham-O. He was not immediately available for comment.

Goodwin Procter has represented Wham-O in some of its infringement cases of various manufacturers. In 2007, Wham-O won a $6 million verdict against SLB Toys USA Inc., for infringement of the Slip 'n Slide in a case that involved the water toy's signature yellow color. An appeals court later affirmed the award. The Goodwin Procter attorney representing Wham-O in that case was Robert McGahan. He is no longer with the firm.

The case is Wham-O Inc. v. Goodwin Procter, No. BC461721, California Superior Court, Los Angeles. For the plaintiff: Steven Chazen, Law Offices of Steven J. Chazen, Sherman Oaks, Calif.

For the defendant: John O'Connor, O'Connor and Associates, San Francisco.

(Reporting by Leigh Jones)