Comcast should discontinue its claim that Xfinity service "delivers the fastest Internet in America," the National Advertising Division (NAD) recommended today. Comcast should also discontinue certain ads where it claims to have the "fastest in-home Wi-Fi," the group said.

For its fastest Internet claim, Comcast relied on crowdsourced data from the Ookla Speedtest application. An "award" provided by Ookla to Comcast relied only on the top 10 percent of each ISP's download results.

"Although Xfinity offers a variety of speeds at a range of prices and tiers, Comcast’s advertising does not limit its claims to a particular tier," the NAD's announcement said. "NAD determined that the claims at issue in both print and broadcast advertising reasonably conveyed a message of overall superiority—that regardless of which speed tier purchased by a consumer, in a head-to-head comparison, Xfinity would deliver faster speeds."

Though one methodology might be reliable for one purpose, "it may not be sufficient substantiation for advertising claims made in a different context," the NAD said. Ookla's methodology "wasn’t a good fit for the purposes of substantiating Comcast’s overall superior speed performance claim that 'Xfinity delivers the fastest Internet in America,'" the NAD also said.

Comcast's fastest Wi-Fi claim was based on data from Allion Test Labs, but the company used the claim too broadly, the NAD said. "In those advertisements where the claim 'fastest in-home Wi-Fi' reasonably conveyed to consumers the unsupported message that Comcast offers the fastest available wireless access to the Internet, NAD recommended that the claim be discontinued," the group said.

The NAD's decision came in response to a challenge filed by Verizon. Comcast has also made claims in direct-mail advertisements that Verizon is "eliminating its traditional home phone service in certain markets" and that "Verizon is discontinuing its copper-wire based home phone service.” These claims are "potentially confusing to consumers" and should be "discontinued or modified to accurately communicate that Verizon is changing the way it is delivering, rather than eliminating, phone service to consumers," the NAD said.

Comcast previously challenged Verizon's speed claims, leading to a National Advertising Review Board (NARB) recommendation that Verizon change its ads claiming that FiOS fiber service "is rated #1 in Internet speed."

Comcast today said that it “disagrees with NAD’s decision and is appealing to the NARB" but did not provide further comment. Comcast voluntarily discontinued claims that its TV service offers "unsurpassed HD picture quality" in response to Verizon's complaint.

The NAD and NARB are part of the advertising industry's system of self-regulation. The decisions have no legal force, but the NAD says that "advertisers' willingness to support NAD and voluntarily adhere to its decisions helps to ensure an honest and open playing field in advertising."