Bauer, Orange, BSkyB, The Sun, The Guardian, Yahoo and Microsoft are seven of the 21 companies that participated in the survey, representing hundreds of websites.
Mobile display ads, which include banners, text links, tenancies pre and post-roll and in-game, accounted for £14.2m in 2008 - just under half of all mobile ad spend.
Banners accounted for 82% of display ad expenditure, helped by the growth of social networking sites such as Facebook, which achieved mobile growth of 180% year on year. Pre and post-rolls and in-game ads only accounted for 2% of the display market.
Paid-for search advertising on mobile was estimated to account for £14.4m, 50.2% of all mobile spend.
A spike in mobile internet usage was a key driver of growth, from 8.6 million people in December 2007 to more than 11 million in December 2008.
Better handsets also contributed, with iPhone users seven times more likely than average to browse daily for news and information. More UK media agencies have also appointed dedicated heads of mobile.
Jon Mew, head of mobile at the Internet Advertising Bureau, said: "This is a landmark moment for mobile media. The study is a UK first and makes mobile a credible media channel. The advertising industry is taking mobile more seriously because advertising opportunities are starting to mature. Content on mobile has got better and more publishers are driving individuals to look at content via their mobiles."