Leaders of the conservative advocacy group FreedomWorks sided today with the Cato Institute in its feud with Charles Koch, the billionaire conservative who helped found the libertarian think tank.

FreedomWorks condemned lawsuits filed by Charles and David Koch seeking to expand their control over Cato in a statement signed by the group’s leaders, former House Majority Leader Dick Armey (R-Texas) and C. Boyden Gray, and its president, Matt Kibbe.

“It is clear that this hostile takeover bid, if successful, will do irreparable harm to the credibility of Cato, and equally important, will undermine our community’s intellectual defenses,” they wrote. “It is our hope that the parties at Koch Industries will reconsider their ill-conceived actions.”

The statement came just days after the Koch brothers filed a second lawsuit in federal district court in Kansas against Cato, seeking reversal of what they called a “board-packing scheme” to weaken their influence over the organization.

In March, the brothers asked the same court to enforce an old agreement that would give them control of the four-person shareholder group that governs the institute, as well as the authority to appoint a majority of a separate, 16-member board.

A spokesman for the Koch brothers didn’t return Roll Call’s request for comment.

Cato scholars have spent the past month waging an aggressive campaign to persuade conservative leaders to condemn the Koch brothers’ actions, but few have weighed in publicly.

Crossing the Koch brothers, two of the nation’s biggest conservative political donors, is risky. However, FreedomWorks, a libertarian advocacy group that has claimed the tea party banner, is somewhat insulated. The Kochs have not contributed to FreedomWorks since 2003, when it split from the Koch-backed Citizens for a Sound Economy, Kibbe told Roll Call.

The second lawsuit was the last straw in an embarrassing family feud gone public, he said.

“They have to stop,” Kibbe said. “If your goal is defending a free society, if your goal is fighting for limited government, I can’t possible see any plausible reason for doing what they’re doing.”

Cato scholars fear that the brothers intend to fold the nonprofit into their empire of Republican groups because of their past support for groups such as Americans for Prosperity, which played an active and crucial role in 2010 by helping Republicans secure control of the House and gain seats in the Senate.

They have also taken their pleas for independence to reporters and op-ed pages of Washington, D.C., newspapers. On Monday, Joseph Coon, the Cato Institute’s director of sponsor services, trumpeted the launch of a new blog, KochVCato.com.

“I wouldn’t be surprised if a lot of people feel the same way that FreedomWorks does but don’t want to say anything critical about the Kochs,” said Michael Cannon, director of health policy studies at Cato. “Because even I don’t want to say anything critical about the Kochs.”