The U.K.'s largest commercial radio network, Global Radio, is set to launch an interactive chart show based on iTunes downloads and airplay data from Independent Local Radio (ILR), June 14.

The Sunday night "Big Top 40 Show" will be broadcast live nationally on Global stations between 4 and 7 pm, hosted by Rich Clarke and Kat Shoob. Numbers 40-11 on the chart will be compiled from downloads and airplay data, while the top 10 will be determined by downloads only.

A top 10 will be introduced at the start of the show and updated regularly as new downloads are tallied, culminating in a full-track playback of the final 10 that leads up to the show's end at 7 p.m. By purchasing songs during the program, listeners are able to influence which order the 10 songs appear in the final countdown.

In its current Hit 40 U.K. format -- which uses airplay data from Nielsen, and physical and download sales data from the U.K.'s Official Charts Company -- the show is networked to 127 stations in the Global network with an audience of 1.4 million (according to RAJAR). Upon conversion to the new format, the show will extend its reach to 142 stations, which Global expects to reach 2.1 million listeners.

"Everybody here is extraordinarily excited about the potential of involvement in the first real-time chart, where the listener can do what the viewer does for American Idol -- they can help create a star," says Global Radio director of broadcasting Richard Park.

According to Park, "with 96% of sales in the U.K.'s official chart now being from downloads alone, it's important we reflect the new future of purchasing music, and there is no more significant partner than iTunes."

The Big Top 40 Show will also feature music news, new artist recommendations and interviews. The Official Charts Company declined to comment on the new format.