On top of the infighting among animal agriculture groups over a proposed bill to set national welfare standards for egg production — which has pitted the egg industry against pork, beef, and poultry — there is some conflict among animal rights groups as well.

The Humane Farming Association, a California based anti-factory farming group, is trying to convince lawmakers to vote against what it calls the “rotten egg bill,” which has been proposed in both chambers, most recently as an amendment to the 2012 Farm Bill in the Senate.

As the Senate began debate on the Farm Bill Wednesday, the group ran a quarter-page advertisement in the Washington Post calling the egg bill a price-fixing scheme that would “deprive states of the right to enforce anti-cruelty laws which prohibit battery cages.”

The legislation to slowly phase in “enriched colony housing” for laying hens, which would double the space for each bird, was the result of a landmark deal struck between the United Egg Producers and the Humane Society of the United States, two groups who had been fighting bitterly over state egg initiatives for years. The compromise seeks to give egg producers regulatory certainty, while fulfilling HSUS’ goal of giving hens more space.

But HFA and other local groups are angry that standards might preempt state laws that seek to go above and beyond the welfare standards in the HSUS-UEP deal.

“The egg industry is seeking to establish egg factory cages as a national standard that could never be challenged or changed by state law or public vote,” said Bradley Miller, national director of HFA. “This bill would preempt state laws, such as California’s Proposition 2, and is a direct assault upon egg laying hens, voters, and states’ rights.”

The debate over federal standards has put some animal rights groups — like HFA, Friends of Animals, United Poultry Concerns, Action for Animals, and Last Chance for Animals — squarely alongside the National Cattlemen’s Beef Association, the National Pork Producers Council, and American Farm Bureau in opposition to the bill.

“There is no such thing as an ‘enriched’ battery cage,” said Priscilla Fera, president of Friends of Animals. “This is an outrageous attempt by the egg industry and its cohorts to enrich themselves at the expense of laying hens and the public at large.”

Sen. Dianne Feinstein (D-CA) first introduced the egg bill last month, with Sens. Richard Blumenthal (D-CT), Scott Brown (R-MA), Maria Cantwell (D-WA.), Jeff Merkley (D-OR), David Vitter (R-LA) and Ron Wyden (D-OR) as cosponsors, and Sens. Susan Collins (R-ME), John Kerry (D-MA), Joe Lieberman (I-CT), Patty Murray (D-WA), Bernie Sanders (I-VT) and Robert Menendez (D-NJ) are also supporting Feinstein’s effort to add the measure to the Farm Bill.

Though the amendment is backed by a variety of egg industry, animal welfare, consumer, and veterinary groups — like the American Veterinary Medical Association, Mercy for Animals, Farm Sanctuary, and the National Consumers League — it is not clear whether Feinstein will have the votes she needs to attach the bill.

Livestock groups remain vehemently opposed to the legislation, calling it the “farm takeover bill,” and it’s not yet clear if Feinstein and her colleagues will succeed in bringing the amendment to the Senate floor for a vote.

Senate Majority Leader Harry Reid (D-NV) is keeping tight control of the amendments allowed for consideration. Of the more than 200 amendments that have been filed, the Senate considered two on its first day of debate and negotiations over which amendments will see the floor are ongoing. Debate is set to resume at 9:30 a.m. EST today.