The Advertising Standards Authority (ASA) has rapped T-Mobile over claims made in a recent press ad and brochure, following a challenge by rival operator 3.
The ads were part of T-Mobile's 'You won't find more minutes for £30. Guaranteed' campaign in which the press ad stated: 'We've already searched the other four networks.'
Small print at the top added: 'Compared to Sim-only or 18-month plans for new customers, excluding promotions.'
Hutchison 3G, which owns 3, described the claims as misleading, because it believed its Mix & Match 1100 tariff, which offers up to 1,100 voice minutes for £27, is more competitive.
T-Mobile argued that 3's Mix & Match 1100 plan is not comparable to its Combi 30 plan, on which its ad campaign is based, because Combi 30 offers a fixed number of minutes and texts whereas Mix & Match 1100 offers a variable allowance.
The operator said it believed the plans should be compared on a like-for-like basis and that, in order to compare them fairly, the 400 text messages offered in the Combi 30 plan should be taken into account in Mix & Match 1100. Both plans would then offer 700 minutes.
The ASA noted T-Mobile's arguments, but upheld 3's challenge on the basis that the claim on the front of the brochure did not include qualification, and that readers would take it as an absolute claim.
T-Mobile has been told that the press ad and brochure must not appear again in their current form, and to ensure that all available plans are included in future comparisons.
The watchdog also investigated two TV ads based on the same campaign, but did not find them in breach.
Biometrics of more than five million taxpayers taken by HMRC
Central Bank of India forced to make banks take basic security more seriously
Qualcomm planning to use TSMC's 7nm process to make fast and power-efficient rival to Intel
Voice assistants in smart homes will reach 275 million in five years' time, and Amazon is in pole position