The singers will also be joined by Hot Chip, Kelis, Friendly Fires and Frankie Goes To Hollywood's Holly Johnson at the event, which takes place at London's Victoria Park between June 15 and June 17.
Friendly Fires announced: "We're thrilled to be playing the main stage of Lovebox this year. Having risen through the ranks after playing a small tent there in 2007, we're proud to again be part of a London summer institution."
Johnson added: "By amazing grace I have survived to perform at Lovebox 2012...My first London stage appearance in the 21st Century... Hollylujah!"
East London radio station Rinse FM, who have partnered up with the event, said it was "only right we team with Lovebox to create the radio experience in the park. It's extra special having the chance to bring our camp to a wider audience in our manor."
The three-day weekender is divided between Friday's "Bang the Box" day with Magnetic Man, Sub Focus and Crystal Castles, Saturday's "sonic mash-up" of headliners and Sunday's polysexual "Out and Out Fierce" day with the likes of Azari & iii and Niki & The Dove.
Last year's Lovebox headliners included Snoop Dogg, Blondie and The Human League.
Tickets, priced between £29.50 and £99, are available now.
> Lovebox music festival 2012 confirms earlier dates
View the full Lovebox lineup below:
Friday - Bang the Box
Big Top (Hosted by Rinse 106.8FM)
Boy Better Know
Digital Soundboys Eastside Carnival
Sub Focus LIVE
Shy Fx + Stamina MC
The Toddla T Sound
The NYC Downlow
Hessle Audio presents:
Picture Music pres Lapalux b2b Dauwd
The Big Top - Hospitality
Camo & Krooked
Fred V & Grafix
The Stockade - Crosstown Rebels present A Rebel Rave
The NYC Downlow (Hosted by Warm & Electric Minds)
Sunday (Out & Out Fierce)
Azari & iii
Nikki & The Dove
Jonny Woo Etc
Second Stage (Hosted by Dalston Superstore)
The Golden Filter
Big Top (Hosted by Gutterslut & Trailer Trash)
Gutter Slut DJ's
Miss Crystal MC
Trailer Trash DJ's
The NYC Downlow (Hosted by Horsemeat Disco)
Jim Stanton and James Hillard
The Stockade - This is…Circus
Kris Di Angelis