
Spotify's new billboard format will see full-screen ads served over the Spotify application once a user has been inactive for five minutes.
The ads will complement 3 Mobile's free Skype to Skype calls campaign on pay as you go campaign.
The billboard will remain in view until the user once again becomes active, such as rolling over the screen, after which it will scroll down into the leaderboard.
3 Mobile will be the first brand to utilise the new billboard size format, together with an accompanying audio ad and leaderboard.
Mindshare was responsible for encouraging 3 to take on the campaign, while Glue provided the creative.
Greg Jarvis, account manager at Spotify, said: "Our new billboard format creates fantastic standout for a brand and it's great to see 3 Mobile looking to make the most of Spotify's ad platform."
Spotify allows users to listen to streaming music for free in exchange for occasional ad interruptions. Users are also able to purchase a premium subscription, which features no advertising.