Facebook is suing several law firms in the wake of another lawsuit by a man who claimed he was entitled to half of the social networking company, according to the Associated Press (News - Alert).

Paul Ceglia sued the company in 2003, a year before Facebook was founded, claiming that the contract to develop software he signed with Mark Zuckerberg (News - Alert) gave him ownership of half of Facebook in exchange for $1,000 to found his own startup.

Facebook’s own lawyers admitted that there was a contract, but claimed that the references to Facebook (News - Alert) were slipped in later. The case was later dismissed. Ceglia is awaiting trial on fraud charges that he forged the documents used in the case.

The company’s lawyers claimed in a new lawsuit that DLA Piper, who represented Ceglia, as well as several other law firms named in the suit, should have known that the documents he claimed entitled him to half of Facebook were obvious forgeries.

Facebook is seeking an unspecified amount of damages from the company in the New York State Supreme Court.

“We said from the beginning that Paul Ceglia's claim was a fraud and that we would seek to hold those responsible accountable," Colin Stretch, Facebook's general counsel, said in a statement. "DLA Piper and the other named law firms knew the case was based on forged documents yet they pursued it anyway, and they should be held to account."

DLA Piper said that Facebook had no basis for the lawsuit. Peter Pantaleo, the general counsel for the firm, said that DLA Piper was only involved with the case for 78 days.

"Facebook and Mr. Zuckerberg claim that they were damaged in those 78 days, yet a mere 10 months after DLA Piper withdrew from the case and while the litigation was still pending, Facebook went to market with an initial public offering that valued the company at $100 billion,” he said.