The Federal Trade Commission sued PepsiCo on Friday for offering preferential pricing to a large retailer, whom a source familiar with the matter confirmed was Walmart.

"Much of Walmart’s market dominance can be attributed to its use of this illegal and anti-competitive tactic," says Stacy Mitchell

Company’s conduct has forced competing retailers, including convenience stores, to pay higher prices, agency says

According to the FTC’s complaint, Pepsi has been providing unfair pricing advantages to one of its largest customers—a major big box retailer—while raising prices for competing retailers and customers. Reuters reports that the retailer is none other than Walmart Inc. WMT , citing a source familiar with the discussions.

The FTC sued PepsiCo on Jan. 17, alleging that it has engaged in illegal price discrimination by giving unfair price advantages to Walmart at the expense of other vendors and consumers.

The FTC has filed a lawsuit against PepsiCo, accusing it of illegal price discrimination by giving preferential pricing to Walmart, disadvantaging other retailers and customers. PepsiCo disputes these allegations,

The US Federal Trade Commission sued PepsiCo Inc. Friday under a rarely invoked 1930s law called the Robinson-Patman Act that bars price discrimination against retailers.

The Federal Trade Commission sued PepsiCo on Friday, alleging that it has engaged in illegal price discrimination by giving unfair price advantages to one large retailer at the expense of other vendors and consumers.

The lawsuit filed in New York alleges the soft drink manufacturer violated the Robinson-Patman Act, a law that went largely unenforced for decades by the federal government. Walmart declined to comment.

The Robinson-Patman Act was passed in 1936, but the federal government stopped enforcing it during the deregulation of the 1980s. The FTC resumed its enforcement in December when it sued Southern Glazer’s, the largest U.S. distributor of wine and spirits.

The Federal Trade Commission is suing Pepsi, alleging it has rigged competition by offering unfair pricing deals to a big retailer at the expense of smaller rivals, resulting in higher costs for shoppers.