The Federal Trade Commission and 20 states have sued Dollar General, the nation’s largest dollar-store chain, for persistently overcharging customers at its more than 20,000 stores across the United States.

The lawsuit , filed in federal court in Nashville, cites a Guardian investigation published last December.

“Dollar General has for years engaged in deceptive conduct that harms the very consumers it claims to serve,” said the 95-page legal complaint.

“Although Dollar General promises convenience, low prices, and value, the company has routinely charged customers more at the register than the prices displayed on shelves, price tags, and advertisements. This pattern of inaccurate pricing has persisted for years and affects millions of purchases across the country.”

The lawsuit says the scope of the retail chain’s “pricing misconduct” is “staggering”.

The FTC is the federal agency charged with protecting consumers from deceptive, unfair and anticompetitive business practices.…