LOS ANGELES — A lawsuit filed April 22 in a U.S. district court in Los Angeles claims a marketing campaign for high-fructose corn syrup is false and misleading in stating that HFCS is corn sugar. The lawsuit filed by Western Sugar Cooperative in Colorado, Michigan Sugar Co. and C&H Sugar Co. cites Internet advertising, exhibitions at professional organizations, television commercials, print advertisements and the web sitewww.sweetsurprise.com.

“We stand by the message in our ads and the science behind it,” said Audrae Erickson, president of the Washington-based Corn Refiners Association, a defendant in the case. Other defendants include Archer Daniels Midland Co., Cargill, Corn Products International, Inc., Penford Products Co., Roquette America, Inc., and Tate & Lyle Ingredients Americas, Inc.

The Corn Refiners Association on Sept. 14, 2010, petitioned the Food and Drug Administration to allow manufacturers the option of using “corn sugar” as an alternative name for high-fructose corn syrup. The F.D.A. as of April 28 had not ruled on the petition.

“Simply, this lawsuit is without merit, and we will vigorously defend our right to petition the F.D.A. to clear up consumer confusion about the name,” Ms. Erickson said.

The sugar companies in the lawsuit argue “corn sugar” already is a name approved by the F.D.A. for a sweetener made from corn starch.

“Impatient for this (F.D.A. petition) approval, the C.R.A. and several of the defendants have already jumped the gun, calling HFCS ‘corn sugar’ in advertising and in pricing sheets for their food ingredient customers,” the lawsuit said.

The sugar companies say the marketing campaign aims to change consumer perception of HFCS by equating it with sugar, especially after some food and beverage companies have substituted sugar for HFCS in their products because of consumer perception of HFCS.

“This suit is about false advertising, pure and simple,” said Inder Mathur, president and chief executive officer of Western Sugar Cooperative. “If consumers are concerned about your product, then you should improve it or explain its benefits, not try to deceive people about its name or distort scientific facts.”

The sugar producers seek an injunction to end the advertising campaign and also seek damages, including compensation for corrective advertising.

The lawsuit also claims scientific studies demonstrate molecular differences between HFCS and sugar and differences in how the human body processes them. The C.R.A. said the American Dietetic Association and the Center for Science in the Public Interest both have said HFCS and sugar are nutritionally and metabolically equivalent.

The lawsuit also claims HFCS is not a natural product and cannot be extracted simply from an ear of corn. The F.D.A., in a letter sent to the C.R.A. in 2008, said it would not object to the use of the term “natural” on a product containing HFCS in which the HFCS is manufactured under a common practice using a specific enzyme.