The Redstone family has launched another salvo at Phillipe Dauman, once among its most trusted lieutenants.

After Viacom Inc., the media company headed by Dauman, released a third-quarter earnings report Thursday morning showing declining profits, National Amusements, the Redstone company that controls Viacom, issued a scathing statement on Dauman.

“It is National Amusement’s view that the current Viacom leadership has failed to articulate a credible long-term plan to reverse the company’s decline,’’ National Amusements said in a statement released several hours after Viacom reported its results.

The media conglomerate, which owns Nickelodeon, MTV, Comedy Central and Paramount Pictures, reported a 27-percent drop in fiscal third quarter profits to $432 million. It blamed the slump on declining television ratings and higher programming and marketing costs. But the results nevertheless beat Wall Street’s modest expectations of Viacom.

The Redstones and Dauman are locked in an ugly dispute over the direction of Viacom and the future of the ailing mogul’s media empire.

National Amusements Inc. is the Norwood-based theater chain and holding company owned by Sumner Redstone that controls 80 percent of the voting stock in Viacom and CBS Inc. His daughter Shari is National Amusements’ chief executive.

Redstone has taken steps to undermine Dauman in recent months, including replacing Viacom board members and changing company bylaws to prevent him from selling off Paramount Pictures.

Dauman responded by suing Shari Redstone, alleging she took advantage of her father’s deteriorating condition in May to remove Dauman from a trust that will control National Amusements — and, therefore, Viacom and CBS Corp. — upon Redstone’s death or incapacity.

The dramatic and complex court case, in which numerous family members and former business associates of Redstone are fighting to secure a slice of his $40 billion fortune, has played out over the past month in the modest Norfolk County Probate and Family Court in Canton.

In late July, the judge hearing the case denied a motion by Redstone and Shari Redstone’s lawyers to dismiss it, and called for the defendants to produce records detailing Sumner Redstone’s health and capacity to make decisions.

Dauman and Viacom have characterized that ruling, along with a similar decision in a parallel case in Delaware, as giving credence to their claims that Shari Redstone is manipulating her father to seize control of the company. On Thursday, Viacom said in a statement that it would continue to move forward, including with the sale of Paramount, despite the controversy.

“Viacom continues to execute on its strategic plan, which is supported by a majority of its independent board,’’ the statement said. “We are looking to the future and executing on the significant growth opportunities we see around the world. In contrast, it is unfortunate that one of our directors feels the need to try to damage the company in response to losses in the courtroom.’’

The Redstone company responded by calling on Viacom’s board of directors — to which it recently appointed five new directors — to crack down on Dauman.

“National Amusements believes that it is time for Viacom’s current directors to stop supporting failed management and start representing shareholders, by allowing the new board to take the reins, and return the company to its position as an industry leader,’’ the company said.

Material from wire services was used in this report. Dan Adams can be reached at daniel.adams@globe.com. Follow him on Twitter @Dan_Adams86.