The multicount criminal case, filed by the Los Angeles city attorney's criminal branch, said Ralphs overcharged on prepackaged and weighed products such as fried chicken, bulk coffee, salads and fish. The chain was fined for similar violations in 2008 and 2009.
Ralphs and parent company Kroger Co. could face fines and penalties of up to $256,000 each.
Kroger spokeswoman Meghan Glynn said the company "takes allegations such as these seriously. We are conducting our own investigation and will take corrective actions as necessary."
During the investigation, conducted between Jan. 20 and March 9 by the Los Angeles County Department of Weights and Measures, inspectors visited 14 Los Angeles Ralphs locations and found 27 overcharge violations, officials said.
"Ralphs is taking money out of their customers' pockets," said Deputy City Atty. Don Cocek, who filed and is prosecuting the case. "It might just be 95 cents, but if you add that up over the number of stores they have times the number of times they sell that item times 365 days a days a year, this becomes a huge ripoff."
Many of the charges were for stores illegally charging for the weight of an item's packaging or for including the ice glaze on frozen products, such as fish, in the net weight. Many prepackaged items were also found to be under the labeled weight, officials said.
During one visit to a Granada Hills location, an inspector bought four packages of fried chicken labeled at a net weight of 30 ounces but found the actual weight of the chicken to be short by 3.5% per package.
At a store on Wilshire Boulevard in L.A., an inspector bought a self-service salad and found that the store failed to deduct the weight of the packaging when calculating the purchase price.
The lawsuit lists 14 counts of false and misleading advertising, 18 counts of unlawful computation of value, nine counts of selling prepackaged commodities in less quantity than represented and 18 counts of false labeling. All charges are misdemeanors.
At a news conference Tuesday afternoon at the Ralphs in downtown L.A., spokeswoman Kendra Doyel said she wasn't sure why the chain was being singled out because "our industry faces these challenges every day."
"There's absolutely no malicious intent in this situation whatsoever," she said. "It would be an oversight."
Ralphs was previously issued notifications after package inspections and test purchases showed multiple violations. It was fined $6,500 in 2008 and $10,400 last year.
Cocek, the deputy city attorney, noted that city officials often will fine a company "and hopefully that notice will correct and resolve the problem," he said. "But in this case, it didn't seem to work."