The Advertising Standards Authority (ASA) has issued sanctions to two broadband providers - banning adverts from BT and TalkTalk respectively.
According to the industry regulator, both companies risked misleading consumers through their advertising content - which has been banned in its current form.
The BT advert, which appeared on TV and in the print media, claimed that the firm's broadband and home phone bundles were available "free for six months".
However, this failed to account for the fact that line rental payments - which must now be factored into any broadband deal pricing - apply from the first day of the contract.
The television ad said BT broadband and calls were priced from "just £13 a month plus £14.60 for a BT line. And now free for six months".
The ASA ruled that this gave the misleading impression that line rental was included as part of the discount promotion.
"Line rental was in fact payable from the start of the contract and this was not made clear in the ads," the ASA stated.
Where TalkTalk is concerned, the banned advert related to TalkTalk's YouView IPTV service, which launched in autumn 2012.
In the ad, the broadband provider explained that higher-tier broadband package subscribers receive a free YouView box, which is "usually/normally £299".
However, a complaint was received from a rival service provider, because the units had only been on sale for six days when the advert was released.
The ASA upheld the complaint, agreeing that one week was not a sufficient period of time for a 'generally sold at' price to be established.
"We also noted that TalkTalk had not provided any evidence to show that any YouView boxes had been sold for £299 when the press ad appeared," the regulator stated.
"Because we considered that the product had not been available to purchase for a sufficient period of time to show that the product was normally or usually sold at £299, we concluded that the ads were misleading."