The portal - an online content platform - is available to Orange users through their mobile phones. Brands including Jaguar, Peugeot, Xbox and United International Pictures' new film Miami Vice are among those set to appear on banner ads within the portal.
Customers accessing Orange World via Nokia, Motorola and Samsung phones will be able to see the ads, which the operator is using to test what kind of ad offerings work best on mobile portals.
To date, most mobile advertising has concentrated on SMS or MMS (multimedia) messages sent directly to people's phones.
All of the UK's operators, including Vodafone, 3 and O2, are experimenting with advertising via mobile owing to a growing demand for mobile content.
Mobile TV and video clips are increasingly popular with mobile phone users and operators are keen to monetise that content.
Currently, users have to pay to download content via mobile. If advertisers came on board they could shoulder the costs covered by users, thereby removing one of the factors that can discourage users from going online via mobile.