BT has been instructed to change part of the advertising campaign for its super-fast Infinity service.
The Advertising Standards Authority (ASA) has upheld two complaints brought by rival broadband provider Virgin Media, in a development set to increase hostilities between the two parties.
Virgin Media initially complained about the wording of a BT advert, which read: "Most of our customers are already seeing at least three times faster speeds."
The ASA said that while this may be true of BT's fibre customers, the majority of BT's UK broadband subscribers still rely on ADSL networks, and have therefore not experienced this service boost.
Virgin Media successfully argued that the advert gave the impression that most BT customers subscribe to its Infinity service, when this is not the case.
Meanwhile, the cable broadband specialist raised a second complaint about the ad, arguing it was not clear enough that BT Infinity has limited availability.
BT is currently investing £2.5 billion upgrading its network to support fibre broadband services, but at present, many areas of the UK remain without access.
As such, the firm accepted the ruling, conceding that while BT Infinity is rapidly rolling out, it is not yet 'widely available'.
BT explained that the ASA wanted this to be made clearer in any future advertising.
But a spokesperson for BT could not resist the opportunity to hit back at its rival Virgin Media, stating: "While we accept this point, we see this as a minor point of clarification, particularly when compared with recent broadband claims upheld against Virgin."
Back in June 2011, the ASA shut down Virgin Media's Stop the Broadband Con advertising campaign, after deciding it had the potential to mislead customers.
The ads criticised broadband providers for their misleading advertising practices, but according to the regulator, Virgin Media was itself committing same offence.
Eight points of objection were raised by BT and Sky, all of which were upheld by the ASA.