Federal officials have been so slow to implement new food safety laws that a federal judge finally had to order the Food and Drug Administration to speed it up.

But the agency isn't alone in delaying the complicated rule. The onion lobby has been aggressively calling for an exemption that would require growers to clean up their act -- literally.

Onion growers argue a requirement that irrigation water contain less than a set limit of E. coli bacteria could put them out of business, and are seeking an exemption for onions and other produce with a low risk of food-borne illnesses, according to the Sunlight Foundation.

The watchdog group examined the influence of produce groups and outside groups in delaying the 2010 Food Safety Modernization Act, and found significant pressure from groups with an interest in delaying the rule.

"Though the law passed in 2010, may of its key provisions are stuck in the regulation-writing process, where the influence of food industry groups appear to far outweigh that of consumers," the Sunlight Foundation said.

Because onions have layers of skin, and irrigation water doesn't touch the vegetable itself, they and other low-risk vegetables shouldn't have to comply with the costly rules, say the Idaho-Eastern Oregon Onion Committee and National Onion Association, who have been lobbying for the exemption.

The groups signed on to a letter by United Fresh Produce Association, the lobby representing produce growers, asking the FDA to extend the comment period for the new law, which it did. The agency now has a June 2015 deadline for publishing the final regulations -- more than four years after it was signed into law.