The advertising industry’s self-policing body says Verizon should stop claiming its FiOS TV service has the best picture quality because the claim isn’t based on a side-by-side test.

Comcast, the country’s largest cable company, challenged Verizon Communications’ claim and asked the National Advertising Division of the Council of Better Business Bureaus to investigate it.

The NAD said Thursday that it found that Verizon’s claim was based on interviews with people about their perception of the cable TV service they had at home, and it didn’t take into account that people watch different types of shows and have different sizes and types of TVs.

Ideally such a claim would be based on a comparison in a controlled environment, the NAD said.

Verizon said it would consider NAD’s recommendation.