The Federal Trade Commission and 20 states filed a lawsuit on Monday against Dollar General, alleging deceptive pricing practices. 

Over a period of years, Dollar General had repeatedly mislabeled prices, overcharged consumers and failed to correct the issue despite the company being aware of the problem, according to the complaint. 

Dollar General disputed the claims, saying in a statement that its goal is "100% accuracy between shelf and register prices in every store." 

"As with other retailers and despite our policies and procedures, occasional price discrepancies can occur. When that happens, our store teams are instructed, empowered, and expected to make things right for the customer. In recent years, we have enhanced our price-accuracy processes and remain committed to continuous improvement," the company said. 

Dollar General operates more than 21,000 stores nationwide and markets itself as a low-priced alternative to large discount and big-box retailers. Low- and fixed-income customers rely on the stores, the FTC said in an announcement of the lawsuit. 

According to the FTC, thousands of Dollar General stores have taken advantage of vulnerable shoppers by extracting millions of dollars in unlawful overcharges with insufficient safeguards to prevent the practice. The company received "tens of thousands" of complaints from consumers across the country about the problem, and Dollar General is aware of the complaints. 

"Despite being made aware of the problem, Dollar General has failed to implement policies and practices to adequately address the problem," the FTC said. 

Dollar General said in its statement that it will defend itself "vigorously" against this litigation.

"We remain ready and willing to engage in reasonable, meaningful discussions to resolve this matter while keeping our focus on what has always been at the heart of Dollar General – serving our customers and the communities we call home. That commitment has not changed and will not change as we navigate this matter," the company said.