An advertising review board has told AT&T that it should either stop advertising U-verse as the "Fastest Internet for the price" or make it clear to consumers that the claim refers to a 3Mbps service, one of the slowest speeds AT&T offers.

AT&T offers Internet downloads of up to 3Mbps for $29.95 a month for the first 12 months with higher prices thereafter. U-verse customers can pay more to get up to 45Mbps:

After a complaint from Comcast, the National Advertising Division (NAD) of the Council of Better Business Bureaus agreed that the "Fastest Internet for the price" claim is misleading. "NAD recommended that AT&T either discontinue its 'Fastest Internet for the price' claim or modify the claim by ensuring that consumers understand that the claim is based on a comparison of pricing for 3.0 Mbps service," the organization said in an announcement Monday.

3Mbps is lower than the Federal Communications Commission definition of broadband, which requires broadband download speeds to be at least 4Mbps. The FCC has proposed raising the broadband standard to 10Mbps, a move that AT&T has opposed. AT&T also offers DSL service with a maximum speed of just 768Kbps.

Comcast also complained about AT&T describing its U-verse Internet service as "reliable." The NAD concluded that AT&T can support its claim of reliability, but should still "discontinue two television spots or modify the spots so that they no longer convey the unsupported message that U-verse itself is the reason for the vastly improved quality and speed of Internet service."

Comcast's third complaint centered on AT&T advertising "up to 45Mbps." The NAD determined that AT&T can support this claim as well, but it recommended some changes to advertising because the speed is not widely available in all markets.

"NAD recommended that where the advertised tier of service is available to less than 50 percent of the consumers in the geographical area where the advertising appears, AT&T should modify its advertising to clearly and conspicuously disclose such limitations through the use of explicit qualifying language—e.g., 'up to 45 Mbps may not be available in your area,'" the NAD said. The NAD also recommended that AT&T "clearly and conspicuously disclose that consumers may not receive the advertised maximum speeds when two or more HD streams are being viewed in the household."

The NAD is part of an industry self-regulatory process. AT&T said it will take NAD’s recommendations into consideration but is "very disappointed, however, with NAD’s decision recommending additional disclosures be made regarding theoretical bandwidth reductions for U-verse users engaging in very specific and rare combinations of behaviors... We believe this kind of disclosure overload does not contribute to consumer understanding of the product offering, but rather detracts from it.”

This isn't the first time AT&T and Comcast have clashed over advertising. In 2012, the NAD told Comcast that it should stop calling AT&T's U-verse network "a bunch of old phone wires" and stop calling its own hybrid fiber-and-cable network an "advanced fiber optic network." Comcast continued disparaging AT&T in advertisements, leading to another warning from the NAD in October 2013.