Deb Thomas, of Clark, Wyoming, speaks at the "Stop the Frack Attack People's Forum" to discuss how people living near oil and gas fields are impacted by fracking, in Washington May 22. (Gary Cameron/Reuters)

In an unusually public dispute, about 70 environmental groups Wednesday scolded one of their larger brethren, the Environmental Defense Fund (EDF), for joining with a group of energy companies that support hydraulic fracturing.

The group of mostly small, local environmental organizations, joined by actors Mark Ruffalo and Debra Winger, as well as Robert F. Kennedy Jr., accused the EDF of “greenwashing” the practices of oil companies that engage in “fracking” of shale rock to extract oil and natural gas.

In a letter to EDF’s president, Fred Krupp, the groups said they were dismayed to see his group become a founding member earlier this year in the Center for Sustainable Shale Development (CSSD), along with Chevron and Shell oil companies, the Heinz Endowments, the Pennsylvania Environmental Council and others. On its Web site, the group says it is an “unprecedented, collaborative effort of environmental organizations, philanthropic foundations, energy companies and other stakeholders committed to safe, environmentally responsible shale resource development.”

Many environmentalists oppose fracking because of the large amounts of water and some of the chemicals that are used to remove the fossil fuels.

In a conference call, the environmental groups said EDF is participating in an organization that is not committed to tough regulation of fracking or the promotion of solar, wind and other renewable forms of energy.

“We feel it is important that the press and the public clearly understand that neither EDF nor CSSD represents the environmental and public health communities on the subject of shale oil and gas extraction,” the groups wrote.

Eric Pooley, EDF’s senior vice president for strategy and communication, said the organization “has been fighting for strong regulations, strong oversight and penalties at the state level.”

“Being part of CSSD,” he added, “does not mean we’re not for regulation. It never has. We’ve never said it. We never will.”