Legislators in Iowa—the largest egg-producing state in the US—have passed a law forcing retailers to sell eggs produced in battery cages.

The law, passed by both legislative chambers in Iowa, applies to retailers involved in a food assistance programme run by the federal government for low-income mothers and children.

Under the new legislation, any retailer selling ‘specialty eggs’—eggs advertised as cage-free, free range or enriched colony—under federal food assistance programme is also required to sell ‘conventional eggs’ which are defined as ‘eggs other than specialty eggs’.

While the majority of eggs produced in US each year comes from traditional cage units, there has been a trend recently to move away from caged hens.

The legislation could affect retailers like Walmart that have already committed to going cage-free by 2025.

The new law has upset animal welfare campaigners, but supporters of the new law have defended the move.

Republican politician Lee Hein said: “I believe that we don’t need to bow down to the pressure of the animal rights groups, which are maybe growing, but are still a small segment of the population. I firmly believe that the regular Iowans want a choice.”

Humane Society of the United States (HSUS) acting president and chief executive Kitty Block said the ‘factory farm lobby has reached a new low’.

She added: “This bizarre legislation would actually force many grocery stores to sell a product that businesses and consumers are increasingly rejecting; eggs from caged hens.”

According to Block more than 200 companies in the US have committed to going cage-free, including Walmart, Subway, Costco, McDonald’s, Burger King, Nestle, Sodexo, Aramark, Heinz and Starbucks.

Cage eggs sales have also fallen to 85%.

She said: “Virtually every major food retailer has adopted policies requiring explicitly cage-free conditions – a vast improvement over cage confinement. These companies are simply listening to their customers, who are rightly concerned about the enormous animal welfare and food safety problems these cages cause.”

According to Block ‘factory farming corporations try to stop any regulation of their cruelty by saying that the free market should decide’.

She added: “But now that the free market, state legislatures and courts are deciding against the worst factory farming practices, the corporations are changing their tune and demanding that the Government bail them out, taking market share away from cage-free farmers.”

Republican Dan Zumbach said the new legislation provides people taking part in the food assistance programme with a lower-cost choice of protein.