The survey, which was conducted online during April and May 2008 by Ipsos Mori, found that 14.5m people now listen to the radio via the internet, up 2.5m since last November.
Other findings include 9.4m people listening to the radio either live, or on listen again services on a weekly basis. However listen again services don't necessarily have an impact on the amount of radio that is listened to, with three-quarters questioned agreeing that it didn't make them listen to more radio.
Podcasting has also become more popular, with downloads increasing to 6m from 4.3m, while 3.7m say they listen to them each week.
Radio listening has also been improved by podcasts, with 15% admitting to listening to more radio since downloading podcasts. Another notable factor shows that 39% now listening to radio programmes that weren't listened to previously.
However, iTunes is the most popular choice for downloading podcasts, with almost three-quarters of podcast users downloading them from the Apple software.
Christel Lacaze, research manager at Rajar, said: "This survey gives a unique insight into the behaviour of the online/offline audio community and the impact of new audio delivery formats on traditional live radio listening."
Advertising faired well in the survey, with over half (53%) of respondents claiming they would be interested in downloading podcasts containing advertisements, if the podcasts were free.