The ads, promoting Sky phone and broadband services, stated: "Cut your broadband and phone bills by around half with Sky."
A table was shown comparing the cost of Sky’s services with Virgin Media and BT, and the savings available to its competitors' customers.
Virgin Media challenged whether the comparison misleadingly exaggerated potential savings by not factoring in the price difference between Sky TV and Virgin Media TV, as well as the cost of paper billing, which was an optional charge for its customers.
It did not believe that the claim that Virgin Media and BT line rentals are 20 per cent more expensive than Sky could be substantiated. It also challenged Sky's claim of truly unlimited broadband, suggesting it unfairly implied Virgin’s broadband was subject to restrictions.
Sky argued that paper billing was a valid charge to include when making savings comparisons.
It said its customers had the option of free paper billing and the ad’s small print clarified this cost was included in the comparison.
The claim referring to truly unlimited broadband aimed to highlight that Sky customers could upgrade to a product that was not subject to a traffic management policy for an extra £5 a month.
It said a Virgin Media customer looking for a similar package would have to pay £42.45 a month.
The ASA understood the ads targeted existing Sky TV customers whose telephone and broadband services were supplied by Virgin or BT, and the savings claims were based on this assumption.
As a result, the ASA disregarded Virgin Media’s concern that the ad intended to urge its TV customers to switch to Sky.
However, the watchdog considered readers would infer from the claim that Virgin Media and BT line rentals are 20 per cent more expensive than Sky, meaning that Virgin’s line rental alone was 20 per cent more expensive, and on this point the ad was misleading.
The ASA told Sky not to repeat the claim in future advertising.