Washington ? Charles and David Koch are among the top givers nationwide to groups that promote conservative policies in Washington, according to a study released Thursday.

The Koch brothers, who own Wichita’s Koch Industries, gave more than $20 million to groups that further conservative thought in academia, politics and media from 1999 to 2001. That’s according to an analysis of IRS documents done by the National Committee for Responsive Philanthropy, a liberal Washington, D.C., group that tracks conservative foundations.

The donations, given through the Charles G. Koch, David H. Koch and Claude R. Lambe charitable foundations, ranked seventh, eighth and 13th among all foundations that give to conservative groups, making the Kochs one of the most influential conservative families in America, said Jeff Krehely, deputy director of the philanthropy group.

“It’s certainly an effective apparatus the Koch family has set up” to advance their views on economics, liberty and the way the world ought to be, he said.

The Kochs have long been known in Washington policy circles as major donors to causes that push for less government regulation and greater reliance on the free market to determine the choices of individuals and businesses.

The Koch family foundations try to advance the causes of peace, prosperity and social progress in the world, said Mary Beth Jarvis, a spokeswoman for Koch Industries.

Organizations they’ve founded and funded produce numerous position papers and appear frequently in media promoting those positions. Those groups include Washington policy think tanks such as the Cato Institute, academic centers such as the Mercatus Center at Virginia’s George Mason University and environmental groups such as the Foundation for Research on Economics and the Environment in Montana.

By funding these groups and maintaining a consistent message for decades, the Kochs, and other conservative donors, have managed to shift America’s policy debate.

Koch-funded groups “market their ideas, they focus long-term, and they cultivate new leaders” by supporting projects and getting them attention, said Rick Cohen, president of the philanthropy group.

But Cohen’s group and others on the left are concerned that the foundations funding conservative organizations, though operating under guidelines established for charitable nonprofit groups, serve corporate, not public, interests.

John Podesta, former chief of staff for President Clinton and now head of the left-leaning Center for American Progress, said the Kochs were harming Americans by pushing policies that harm the environment and put more of the overall tax burden on working families, hiding behind groups that disguise their corporate interests.

“People need to understand what’s going on,” said Podesta, who spoke at a news conference announcing the study results.

But Jarvis said all the Kochs were doing was supporting ideas that will make for better public policy.

“We want to integrate theory and practice such that scientific methodology trumps partisanship, slogans and short-term thinking,” she said.