Adverts for Vodafone broadband have been banned for misleading customers over speeds and reductions in bills.
The television and radio ads, featuring actor Martin Freeman, stated: “Vodafone guarantee your home broadband speeds or money off until it’s fixed.”
But the Advertising Standards Authority (ASA) upheld complaints – including from rival BT – that the claims could not be substantiated.
Vodafone said it was “disappointed” by the ASA’s ruling to ban the ads.
The ads featured Mr Freeman playing an online video game, only to have his internet “drop out” at a key moment.
His opponent in the game tells him to “just get Vodafone” and on-screen text tells viewers they can claim a discount if speeds are below certain thresholds.
And Vodafone’s website stated: “Our Ultimate Speed Guarantee means you get the best broadband speed available to you, or we’ll give you a discount off your monthly bill until we can get you there.”
But the ASA said consumers would interpret the ads to mean that Vodafone could guarantee minimum speeds fast enough to avoid common issues such as buffering.
The regulator said customers experiencing buffering and lower speeds might not qualify for the discount on bills.
The ASA said that it had told Vodafone to ensure its advertising did not mislead customers in the future.
A Vodafone spokeswoman said the company was “disappointed” by the ruling and added the ASA had “misunderstood” the offer.
She said the guarantee “is still unmatched in the market as no other major brand offers a promise like this across their entire range, nor do they apply discounts directly to customers’ bills if they don’t deliver”.