Mobile internet usage will grow 39 percent in Western Europe in 2014 from 13 percent in 2008, according to a new report by Forrester Research released today. That means that more than a third of consumers in Western Europe will access Internet from their mobile phones by 2014, great news for mobile advertisers.

At the end of this year, Forrester expects mobile Internet penetration to reach 17% in Western Europe — the same adoption rate for the PC Internet a decade ago, according to Forrester analyst Thomas Husson.

“Consumers who have a flat-rate data bundle spend more and more time on the Internet from their mobile phones, brands begin to launch their mobile Web presence to monetize these growing audiences and engage with their customers via more relevant mobile content and services, which in turn attracts more and more consumers to unlimited mobile Internet tariffs. The current economic climate will lengthen handset renewal cycles, foster the development of low-cost offerings, and boost the uptake of SIM-only contracts.

At the end of 2009, mobile Internet penetration will reach 17 percent in Western Europe, the same level of adoption that PCs with Internet access had in 1999, which Husson described as being a critical mass. “In the next decade, the mobile Internet will replicate the success story of the PC-based Internet as social networks, widgets, search engines or company websites adapt for mobile presentation,” Forrester reports.

Hussan writes that the “iPhone is just the tip of the iceberg” and that many other devices and services will enable the surge of mobile internet usage in Europe over the next five years.