Mobile operator O2 UK has been left blowing bubbles after losing a four year battle against rival 3 over the usage of bubbles in its advertising.

On Thursday, the European Court of Justice ruled that “O2 cannot rely on its trade mark rights” to prevent the use of bubble imagery in a comparative advertisement for Hutchison-Whampoa’s UK 3G operator.

In 2004, 3 launched an TV advertising campaign for its prepay service, Threepay, in which it compared the price of its services with those of O2. The advert used the name ‘O2’ and moving black and white bubble imagery, followed by ‘3’ imagery and a comparison stating that 3’s services were cheaper in a specific way.

O2 uses bubble images in its own advertising in a host of ways and owns two British trade marks which consist of a static picture of bubbles.

O2’s copyright infringement claim had already been dismissed by the British High Court, but O2 had appealed to the European court.

In other O2 news, the UK operator on Friday announced a deal with BT Openzone to enhance its unlimited wifi package for iPhone customers with access to 3,000 BT Openzone wifi hotspots at no extra cost.

The addition of BT Openzone to O2’s existing arrangement with The Cloud brings the total number of available public wifi hotspots for iPhone customers to over 9,000.