Both Sky and Virgin Media have seen broadband ads banned by the Advertising Standards Authority (ASA) due to the risk of misleading consumers.
The regulator outlawed a Sky Broadband advert following a complaint from Virgin Media, which took exception to a claim made by its rival over network reliability.
Sky said its network "delivers 99.9 per cent average uptime to your local exchange".
The service provider added: "Sky's network is part of your overall connection and other factors affect your overall reliability (e.g. home wiring, equipment and websites you visit). Sky Network areas only."
However, Virgin Media complained that Sky's core network only handles a small proportion of the data flow required to download online content or access a web page.
The ASA agreed, saying it was "concerned" that consumers would not be aware of the distinction between a broadband provider's core network and their overall internet connection.
The regulator added that other factors, aside from home wiring and equipment, can affect the quality of a customer's broadband service.
"The examples did not account for the section from the point of local telephone exchange up to the point the cabling and wiring entered consumers' homes," the ASA added.
"We understood that Sky did not have control over the reliability of this portion of the connection, which could also have an impact on overall reliability."
The ASA banned the advert and told Sky to ensure future claims based on the reliability rate of their core network are fully qualified.
Meanwhile, Virgin Media - which made the complaint about Sky's marketing - also found itself in hot water with the advertising regulator.
The ASA ruled that Virgin Media misled consumers by claiming that they could get "unlimited data" on one of the firm's 3G SIM-only tariffs.
The issue arose due to Virgin Media's practice of throttling the speeds of any consumer who consumes more than 3.5GB of data in any 30-day period.
The firm said that only two per cent of SIM-only customers ever hit this restriction, and see their speeds cut to 384Kb. However, the ASA still ruled against the broadband provider.
"We considered that a reduction in speed from an average we understood to be approximately 6Mb to 384Kb once the limit was reached, was more than a moderate reduction," the regulator noted.
"Because we considered the limitation imposed on speeds to be more than moderate, we concluded that the claim 'unlimited data' was misleading."