According to the latest suit, Katz argued that the other partners could not make decisions without him. "Now, he is actively disputing the ability of the board to take action without him, despite his clear conflict," it says.
Asked Thursday evening about the latest filing, Katz said: "My reaction is that the courts will decide what this is all about, and I'm content with that."
Last week, Katz and Lenfest, who together hold about 42 percent of the company, sued it and publisher Robert J. Hall, alleging that Hall had fired Inquirer editor William K. Marimow without authority to do so.
Philadelphia Common Pleas Court Judge Patricia A. McInerney has scheduled a hearing Tuesday on that claim.
Norcross' suit was filed in Chancery Court in Delaware because IGM and the holding companies used by Norcross and Katz to buy their shares in it are Delaware corporations.
Norcross and three other owners control 58 percent of the company, but he and Katz make up the operating committee that must approve its major business decisions.
Norcross claims that Katz breached their contract by seeking an injunction to reverse Marimow's firing, which Norcross said was the publisher's decision. Hall has contended that Marimow was slow to implement changes at the newspaper.
The suit also accuses Katz of trying to block IGM from hiring investigators and defending itself in the Katz lawsuit.
Doing so was one purpose of Tuesday's partners meeting, according to the suit.
Minutes before it was to start, Katz allegedly sent an e-mail explaining that he could not attend because he was in the Bahamas, and asked for a postponement.
Norcross and the other three partners - Krishna P. Singh II, Joseph Buckelew, and William P. Hankowsky - voted to go ahead with the defense, the suit says. Lenfest, a philanthropist and former cable mogul, disagreed and left the meeting.
The suit was filed a day after the feuding owners met for hours with leaders of the newspaper's largest union in closed-door talks.
"Stay out of it," Lenfest told them, according to an e-mail the Newspaper Guild sent Thursday to its members.
The union leaders' note also said company officials and managers were reading employee e-mails.
"Be very careful what you say" about the ownership dispute, it advised. IGM officials denied reading e-mails except for a small number related to the legal cases.
The meetings with union leaders revealed how bitter and deep-seated the split has been among the partners. One attendee quoted Norcross as saying: "I tried for nine months to buy [Katz and Lenfest] out."
Others said Norcross vowed, "I will not be intimidated. ... I am not leaving."
As recently as two weeks ago, Norcross is said to have told the union leaders, he went to Lenfest with a certified check. He again tried to buy Lenfest's 16 percent share in the company - a stake once valued at $10 million.
Lenfest refused to sell.