A US court has ruled agribusiness giants Archer Daniels Midland and Cargill must answer allegations of false advertising for high fructose corn syrup (HFCS).

Sugar producers accused the companies of trying to "conceal the truth" about HFCS with a national ad campaign about the ingredient.

A court in Los Angeles has ruled ADM, Cargill, plus Tate and Lyle plc and Corn Products International, have to answer the claims.

The sugar farmers' suit has targeted advertising that claimed HFCS is "a natural corn sugar" that "your body can't tell the difference" between the ingredient and common table sugar.

Co-lead attorney for the sugar farmers, Adam Fox of Squire Sanders, said it was an "important win for all American consumers, as well as my clients".

"Judge Marshall's ruling clears the way to allow this lawsuit to proceed so that we can assure an end to the false advertising and make the agribusiness giants behind it answer for their misconduct," Fox said.

The Corn Refiners Association, however, which includes the accused as its members, said the decision was "solely about who is included in the lawsuit". It said the ruling has "no bearing on the merits of the case which are about ensuring that consumers get the facts regarding high fructose corn syrup".

ADM declined to comment on the case and Cargill could not be reached for comment.