The Grocery Manufacturers Association has long served as one of the food industry's biggest and most powerful mouthpieces in Washington.

But over the last year, several companies have broken ranks with the lobbying juggernaut.

Campbell's Soup Co. announced in June it would leave the GMA by the end of this year.

At the end of October, Nestlé announced it would follow suit.

Now, the largest dairy company in the US, Dean Foods, has also decided to leave, according to Politico.

The departures of Nestlé and Campbell's follow a battle over mandatory labeling of genetically modified foods. GMA opposed the idea. Campbell's and Nestlé were in favor.

Other polarizing issues include delays on when new Nutrition Facts labels would take effect.

The White House gave the GMA and other food lobbyists an 18 month extension on those rules earlier this year.

Coca-Cola notably sided with those who wanted to see labels rolled out earlier.

Politico also reports that Mars and other companies are considering an exit.

The fracturing of GMA comes as big food companies face declining market share in the US.

Credit Suisse reported last year that the top 20 food and beverage companies lost a combined $18 billion between 2011 and 2017.

That trend is driven in part by growing demand for organic produce, less processed foods and fewer chemicals, including meat raised without antibiotics.

A spokesman for GMA, Roger Lowe, told Politico that the association is adapting.

"It is not so much an industry divided as an industry that has been tremendously disrupted and is evolving at an unprecedented pace," he said.

He touted other issues that the industry is united on, including changes to the Food Safety Modernization Act and efforts to reduce food waste by reforming language on expiration dates.

Read More:

• The Big Washington Food Fight (Politico)
• Food Company Departures At GMA May Signal Splintering Within Trade Group (Food Dive)