Paul Ceglia, who claims a 2003 contract with Mark Zuckerberg made him a partner in Facebook, said the company's lawyers committed an "egregious and massive violation" of his privacy by publishing his email passwords.
Facebook's lawyers, from Gibson, Dunn & Crutcher, included passwords to Ceglia's web-based email accounts in acourt document filed last week in federal court in Buffalo, New York, according to a filing by Ceglia.
The papers were removed from the public file the next day and Ceglia, in Ireland, changed the passwords, according to his lawyers.
"Counsel's baffling misconduct resulted in Ceglia's email accounts being accessible to the world for 12 hours," his lawyers said in court papers.
They said they intend to ask the court for sanctions and lawyers'fees.
The dispute over Ceglia's emails came as Facebook and Ceglia battle over the exchange of evidence relating to the 2003 contract.
In a court hearing in Buffalo last month, Judge Leslie Foschio ordered Ceglia, 38, to give Facebook access to his web-based emails, which he has said he used to communicate with Zuckerberg in 2003 and 2004.
Zuckerberg has said he signed a contract with Ceglia in 2003 to do work on StreetFax, a business Ceglia was trying to start at the time. The contract made no reference to Facebook, which he started in 2004, according to Zuckerberg.
Facebook, which operates the biggest social-network website, has called Ceglia's claim to a share in the company a fraud on the court.
Closely held Facebook, based in Palo Alto, California, may be valued at US$71.2 billion ($84 billion), according to Sharespost.com, which tracks non-public companies.
At the Buffalo hearing, Gibson Dunn partner Orin Snyder told Foschio that Facebook's outside computer experts had found an image of the genuine contract signed by Zuckerberg on one of Ceglia's computers. It referred to StreetFax but made no mention of Facebook.
