Walmart, which offers some financial services, acts as an agent for money transfer services such as MoneyGram and Western Union.
For years, the FTC said, Walmart’s policy was to issue payments even when fraud was suspected and the retailer failed to take other steps to prevent consumers from being defrauded.
The result was that consumers were defrauded “hundreds of millions of dollars”, the agency said.
Walmart said in a statement it would fight what it called a “factually flawed and legally baseless” lawsuit.
The FTC also said Walmart failed to properly train staff to help them prevent consumers from sending money to scammers.
The FTC said it is asking a court to order Walmart to return lost funds to consumers and pay civil penalties.