Provisions in a pending U.S. House farm bill that would accelerate the review process for genetically modified crops are raising objections from environmental groups and a major grain industry organization.

The provisions would lead to new crops being approved before they have been fully assessed, the Center for Food Safety, an advocacy group in Washington, D.C., said in a letter Tuesday co-signed by other environmental and consumer safety groups, including the Sierra Club.

The legislation would block the U.S. Department of Agriculture from using certain federal laws, such as the National Environmental Policy Act, as a basis for rejecting a proposed seed variety.

The proposal also would impose a one-year deadline for the USDA to assess new biotech seeds, after which they would be automatically approved.

Seed companies have argued that opponents of genetically modified seeds have been needlessly delaying new crops with legal challenges, which threatens to discourage additional investment in the sector.

The environmental and consumer groups argue in a letter to ranking members of the U.S. House Agriculture Committee that the new rules would "make a mockery" of the USDA's crop reviews. The committee is set to finalize the bill Wednesday, and could vote on it this week.

"They've been losing in court, and they're trying to change the rules," George Kimbrell, senior attorney at the Center for Food Safety, said in an interview.

A spokeswoman for a biotechnology trade group representing seed companies such as Monsanto Co. (MON) and DuPont Co. (DD) couldn't immediately be reached for comment.

The National Grain and Feed Association, which represents grain elevators and some of the country's largest grain merchandisers, such as Archer Daniels Midland Co. (ADM) and Cargill Inc., said in a statement Monday that the provisions fail "to encompass the concerns of grain handlers, grain millers and processors, and the food industry over appropriate stewardship practices and other concerns related to premature commercialization of biotech traits."

The NGFA is working with other groups, including the Grocery Manufacturers Association, which includes food companies such as Kellogg Co. (K) and PepsiCo Inc. (PEP), to address these concerns, according to the statement. NGFA officials couldn't be reached for comment Tuesday.

Grain exporters and food manufacturers are sensitive to biotech-seed policies because some countries, such as China and South Korea, are slow to accept crops with genetically modified traits that have already been approved in the U.S.

Mr. Kimbrell said one of the new farm bill provisions would require the USDA to establish for the first time standards to allow a certain low level of genetically modified material in crops deemed not genetically modified.

Opponents of genetically modified crops argue that they cause environmental problems by increasing herbicide use and fostering pests that are resistant to the traits, and have unknown health effects. Proponents of the technology say they help reduce soil erosion and ensure better yields, boosting global food security.