Rival operators Sky and TalkTalk also registered complaints with the ASA over a BT national press advert, which said BT offered "faster broadband even at peak times compared with the ADSL industry average."
Sky and TalkTalk said the basis of the claim was not independently obtained and not adequate for an industry wide comparison, as the data could have been biased if BT had selected telephone lines.
The ASA claimed, whilst the data had been independently obtained by Epitiro, the regulatory body was concerned the information "was potentially subject to inaccuracies based on line length."
"We noted Epitiro had not normalised for line length as part of their methodology."
BT was pleased by one ruling out of seven which went its way, as Virgin and TalkTalk's claim BT does not offer consistently faster broadband speeds than the industry average was quashed by the ASA.
The two rivals believed the press ad's claims were contradicted by a recent independent survey conducted by Ofcom, but ASA rejected this point, as the research did not specifically take into account BT's 20Mbps service.
"When the ads appeared we wanted to highlight our offer of consistently faster web browsing through up to 20Mbps broadband in newly enabled exchange areas; there was no intention to mislead," BT said in a statement sent to IT PRO.
