Sky has been told to pull adverts for its broadband service after Virgin Media suggested they were misleading.
Last year, Sky launched a TV and press campaign which encouraged consumers to sign up to its "super reliable" broadband service.
This phrase was used verbally in the TV commercials and in an on-screen graphic, while the same words featured prominently in Sky's national press ad.
Virgin Media subsequently complained to the Advertising Standards Authority (ASA), arguing the claim that Sky's broadband is "super reliable" was misleading and could not be substantiated.
Sky said it was confident that consumers would understand that the claim was not a comparison with the reliability of other providers' broadband services and that people would take it to mean that its service could be trusted to work well.
Furthermore, it stated that its "super reliable" claim could be substantiated by evidence relating to its overall performance and complaints performance from Ofcom.
However, the ASA dismissed this argument, as Ofcom data showed that while Sky's broadband packages delivered a "similarly consistent connection to that of the comparable packages of their competitors", it did not say they "deliver a more consistent connection".
"We therefore concluded the comparative claim 'Switch to super reliable Sky broadband' was likely to mislead consumers," the watchdog said.
The ASA also noted that while Sky's two fibre packages were deemed by Ofcom to deliver "consistency in all measurable factors of relevance", its ADSL2+ package did so "in all but one factor of relevance".
As a result, it concluded that the non-comparative “super reliable" claim could potentially mislead people, since it implied that all of Sky’s broadband packages were "super reliable" when this was not the case for its ADSL2+ product.
The ASA has therefore told Sky not to show these ads again in their current form and only to use claims that suggest its broadband packages are "super reliable" if it has sufficient evidence to back up this view.