TalkTalk has been censured by the Advertising Standards Authority (ASA) for misleading claims made about its service.
The ASA upheld a complaint from BT over "free broadband" advertised in a TalkTalk brochure.
The ad said: "This year, why not join our Talk3 call plan and get up to 8 Meg (speed depends on proximity to exchange) broadband free!"
BT complained that the ad was misleading since in order to qualify for the "free" deal, customers had to sign up for a minimum contract of 18 months - up from the previous timeframe of 12 months.
BT said this meant that because TalkTalk had increased the burden on the customer, the broadband service could not reasonably be described as free.
Explaining its ruling, the ASA said that "because the contractual agreement of 'Talk 3 with free broadband' was more onerous than that of its call plan-only predecessor Talk 3, we considered that package should be classed as 'new'".