A federal judge has ruled that the antitrust portion of a lawsuit filed by farmers against US biotech giant Monsanto and three of its rivals can proceed.

The lawsuit accuses the biotech seed-marketers of plotting to fix genetically modified corn and soybean prices.

Having thrown out accusations of negligence and public nuisance against the companies, US District Judge Rodney Sippel said that “genuine disputes of material fact” remained in the antitrust portion of the 1999 lawsuit, reported The Associated Press.

Monsanto spokesman Bryan Hurley said the company was pleased that the scope of the case had been narrowed, and said it was confident of a favourable result in the antitrust case.

Monsanto, along with Bayer CropScience, Syngenta and DuPont’s Pioneer Hi-Bred, has denied the claims.

The judge has yet to rule on whether the case should be granted class-action status, meaning it could expand to include more than 100,000 farmers as plaintiffs.