The mobile phone network 3 has won a high court case about an aggressive television campaign it ran two years ago comparing the price of some of its services with a pay-as-you-go deal from O2.

O2, which was acquired recently by Spain's Telefónica for £17.7bn, was furious when the television campaign was aired in August 2004 - not least because it used the group's trademark bubbles imagery. It sought an injunction to have the adverts pulled, but the high court did not accept arguments that the price comparison used was inaccurate or unfair.

The ad said: "On O2 pay-as-you-go, the first three-minute peak-rate call each day could cost you 75p, or with ThreePay that exact same call could cost 15p." It was part of a larger campaign waged by 3, comparing prices between it and all its rival major networks.

O2 sought last year to take the case to the European court of justice, claiming a breach of European rules on price comparisons, but was unsuccessful.

The latest complaint argued that 3 had damaged O2's brand identity. Mr Justice Lewison's written ruling began: "This is a case about bubbles." He said bubbling imagery was commonplace in advertising, citing campaigns for Aero chocolate bars, Oral-B Sonic toothbrushes, Colgate Oxygen toothpaste, British Airways flights and Microsoft Office. There was no possibility of viewers confusing the two networks and 3's campaign had not discredited O2's trademark, he said.

"Within the confines of the comparative advertising directive, advertisers should, in my judgment, be permitted to do what is needed to make the comparative advertising effective." He dismissed a counter-claim from 3 which challenged the validity of O2's bubble trademark.

O2 said it would consider appealing.