What once was a controversy over the relative health benefits of milk has turned into a fight over just who Americans can trust to tell them what is good for them.

The fight started after the Physicians Committee for Responsible Medicine, a group that opposes animal testing and promotes vegetarianism, started an anti-milk campaign in January. The group claimed milk does not improve bone health and can cause a variety of diseases including cancer, anemia and childhood diabetes.

The Washington, D.C.-based Center for Consumer Freedom shot back, releasing information and campaigning against the PCRM, insisting the group is a PETA front group that does business with animal rights leftists.

"This is a sham," said John Doyle, director of communications for the organization. "Their so-called medical advice and health advice is nothing more than a continuation of their extreme animal rights agenda."

Documents prove at least a connection. Tax records show the PCRM is, in part, funded with $430,000 by the Foundation to Support Animal Protection, a group co-founded by the president of People for the Ethical Treatment of Animals, commonly known as PETA.

Neal Barnard, president of the PCRM, does not apologize for sharing money among groups that, he said, promote healthy living.

"We're quite happy to work with groups that might be able to help in the struggle to help people rethink their diets," he said.

Regardless of exactly who the PCRM is, they have had a rocky relationship with the mainstream medical community.

Ten years ago, the American Medical Association accused the group of being "blatantly misleading." More recently, the AMA "registered strong objections" to the group for "implying that physicians who support the use of animals in biomedical research are irresponsible, for misrepresenting the critical role animals play in research and teaching, and for obscuring the overwhelming support for such research which exists among practicing physicians."

But the story doesn't end there. Complicating matters is the money behind the Center for Consumer Freedom. The group is funded by the restaurant, food and beverage industries.

The difference, Doyle said, is that his group readily admits who they are.

"They are trying to create a persona, a legitimacy if you will, and it often works to some level," he said. "They've frequently been cited by the media as a legitimate physicians group, but nothing could be further from the truth. What they are, simply, is an animal rights organization."

A check of recent newspaper articles tends to lend merit to that claim. The Associated Press, which feeds stories to most major newspapers, recently referred to the PCRM merely as "an advocacy group."

And in a Jan. 14 story in The Washington Post about the group's opposition to medical experiments on animals, the reporter wrote that the group is "a health advocacy group that generally opposes animal experimentation."

But the Americans for Medical Progress, who supported animal experimentation in the same story, was described as "formed by pharmaceutical companies in 1991 to counter the animal rights movement."

Doyle said the PCRM has marketed itself as a group of doctors, and succeeded in a media climate that does not allow for the intense investigation of every organization that issues a press release.

Barnard doesn't shy from his group's opposition to medical testing on animals.

"Among the many medical issues we deal with, the abuse of animals is an important thing that needs to be addressed," he said.

On its Web site, the PCRM calls itself a "nonprofit organization supported by approximately 5,000 physicians and 100,000 laypersons."

"Using their own numbers, less than 5 percent of their membership are actually doctors," Doyle said.

Barnard did not dispute the numbers, but said the 100,000 non-doctors are merely "supporting members."

Fox News' Robert Shaffer contributed to this report.