A tempest in a coffee pot is bubbling in the world of “fair trade,” the socially responsible food movement that seeks to lift farmers in the developing world out of poverty by offering them a premium for crops like coffee, cocoa and bananas. And the fight will soon reach your local Starbucks, Wal-Mart and Whole Foods.

Fair Trade USA, the movement’s leading advocate in the United States, angered critics by saying it would cut its ties at year’s end with the main international fair trade group and make far-reaching changes in the sorts of products that get its seal of approval.

The changes include giving the fair trade designation to coffee from large plantations, which were previously barred in favor of small farms. The group is also proposing to place its seal on products with as little as 10 percent fair trade ingredients, compared with a minimum of 20 percent required in other countries.

The group says the changes will benefit more poor farmers and farm workers around the world and make it easier for large corporations to sell fair trade products. Sales of fair trade goods in 2010 were $1.3 billion in the United States and $5.8 billion globally. Fair Trade USA said it hoped to double sales in the United States by 2015.