Both BT and TalkTalk have been censored by the Advertising Standards Authority (ASA) over claims made in their respective marketing.
The broadband providers have seen separate adverts banned by the regulator, which ruled the content of each had the potential to mislead consumers.
BT was rapped by the ASA for a direct mailing advert which claimed Sky would switch off O2's old home broadband service - which it had acquired - in April 2014.
Sky argued that the claim made by BT did not mirror the information it had communicated to O2 customers.
When Sky acquired O2's fixed-line business, O2 subscribers were given the option of switching to a new broadband provider or simply migrating to Sky's platform.
The ASA agreed that BT's warning implied that O2 home broadband customers would see their services switched off altogether in April 2014 - meaning they would lose their internet connection altogether.
"Because we understood that Sky would not switch off the service of O2 broadband customers, rather it would be moved from O2 to Sky, we considered the claim 'Sky to switch off O2 broadband by April 2014' was likely to mislead," the regulator stated.
Meanwhile, TalkTalk's advert was banned for claiming that the firm offers Britain’s "lowest priced" unlimited broadband service.
The ad was in reference to its SimplyBroadband package, which at the time was available for £2.50 per month plus line rental, down from the normal £3.50 per month.
TalkTalk provided a cost comparison for some of the UK's major broadband providers, but failed to acknowledge the low-cost deals on offer with some of its smaller rivals.
The ASA took exception to this, and instructed TalkTalk to make clear the basis of their comparisons in future.
It also instructed the broadband provider to ensure "significant information" relating to price comparisons is given sufficient prominence in its adverts.