Wal-Mart Stores Inc. needs to change its advertising to avoid suggesting its shoppers save an annual $2,500 per family, the advertising industry's self-regulatory body said in a report Monday.

But the report accepted Wal-Mart's claim that its efficiency and size drive down consumer prices across the entire economy, generating that $2,500 savings regardless of where consumers shop.

The National Advertising Division of the Council of Better Business Bureaus singled out what it called implied claims in the retailer's ads that consumers who shop at Wal-Mart can realize that much in savings while people who shop elsewhere do not.

Bentonville, Ark.-based Wal-Mart said in response it never meant to imply the savings were only for its shoppers.

The world's largest retailer said it was pleased that NAD accepted the argument that Wal-Mart saves all consumers money through its overall impact on consumer prices.

"Wal-Mart is pleased that NAD has confirmed that the express claim, 'Wal-Mart Saves the Average Family $2,500 per year,' which was the intended message, was substantiated," Wal-Mart spokeswoman Linda Brown Blakley said.

"We were surprised by NAD's interpretation of an implied claim but confirm, if we use it in future advertising, we would be proud to take their recommendation into account, ensuring that the positive impact we have for all American families is even more explicit," Blakley said.

The National Advertising Division recommended that Wal-Mart modify or discontinue the implied advertising claim.

At issue were television and print ads that showed families taking a vacation or buying a car. NAD said the implied message was that they used money they saved by shopping at Wal-Mart.

Wal-Mart's claim is based on a study it commissioned by economic forecasting firm Global Insight. That study said Wal-Mart has a broad economic impact because of its low prices plus its competitive and efficiency effect on other retailers and the U.S. supply chain.

Global Insight said Wal-Mart's expansion has lead to a 3 percent decline in overall consumer prices for an annual savings of $287 billion in 2006, which averages out to $2,500 per household.

NAD initiated the investigation as part of its role as an independent self-regulator of the advertising industry, an agency spokeswoman said.