By Carey Gillam

(Reuters) - A Republican congressman from Kansas introduced legislation on Wednesday that would nullify efforts in multiple states to require labeling of genetically modified foods.

The bill, dubbed the "Safe and Accurate Food Labeling Act," was drafted by U.S. Rep. Mike Pompeo and is aimed at overriding bills in about two dozen states that would require foods made with genetically engineered crops to be labeled as such.

The bill specifically prohibits any mandatory labeling of foods developed using bioengineering.

"We've got a number of states that are attempting to put together a patchwork quilt of food labeling requirements with respect to genetic modification of foods," said Pompeo. "That makes it enormously difficult to operate a food system. Some of the campaigns in some of these states aren't really to inform consumers but rather aimed at scaring them. What this bill attempts to do is set a standard."

Advocates of labeling say consumers deserve to know if the food they eat contains GMOs, or genetically modified organisms. Many consumer groups question both about the safety and the environmental impacts of genetically modified foods, also referred to as GMOs.

Makers of biotech crops and many large food manufacturers have fought mandatory labeling, arguing that genetically modified crops are not materially different and pose no safety risk. They say labeling would mislead consumers.

Pompeo reiterated those claims, stating that GMOs are safe and "equally healthy" and no labeling is needed.

"It has to date made food safer and more abundant," he said.

"It has been an enormous boon to all of humanity."

But some scientific studies warn of potential human and animal health problems, and GMO crops have been tied to environmental problems, including rising weed resistance. Millions of acres of U.S. farmland have developed weed resistance due to heavy use of crops that have been genetically altered to withstand dousings of Monsanto's Roundup herbicide.

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Ballot measures in California in 2012 and last year in Washington state narrowly lost after GMO crop developers, including Monsanto Co., and members of the Grocery Manufacturers Association poured millions of dollars into campaigns to defeat the measures.

Pompeo said he expects hearings on the bill sometime this summer. The measure would amend the Federal Food, Drug, and Cosmetic Act. One provision would make it mandatory for biotech crop developers to notify the Food and Drug Administration before they brings a new biotech seed to market and receive no objection from the FDA.

Currently, companies typically voluntarily notify the FDA and consult with the agency, but it is not mandatory for them to do so, and the FDA does not conduct independent safety testing of GMOs.

Another provision of the Pompeo measure requires the FDA to promulgate regulations that specify a maximum permissible level of inadvertent GMO presence that is allowed in foods bearing non-GMO labeling.

Backers of mandatory labeling of foods made with genetically modified crops said the bill is a sign that the GMA - the grocers' group - and biotech seed developers fear growing consumer distrust of GMO foods.

"They know that the food movement's power is growing and that labeling is not a matter of if but when." said Colin O'Neil, director of government affairs for the Center for Food Safety, a non-profit group that supports mandatory GMO labeling.

"They are afraid of state action and now they're trying to steal away consumer choice in Congress," he said.

There are currently 66 active bills and ballot initiatives in process in 27 states to require labeling of foods made with GMOs, according to the Environmental Working Group, which is tracking the measures.

Oregon has a ballot initiative set for a vote this fall.

"The vast majority of Americans... consistently tell pollsters that they want the right to know whether there are GE (genetically engineered) ingredients in their food," said Scott Faber, senior vice president for government affairs at the EWG.

(Reporting by Carey Gillam in Kansas City; Editing by Dan Grebler)