The singer will play Sunday's 'Out & Out Fierce' day, alongside Holly Johnson and Patrick Wolf.
Other new acts to be announced are DJs Skream and Benji B for Friday's event, as well as Ms Dynamite and Redlight, who will perform on the Rinse FM stage.
They join already announced headliners Hot Chip, Emeli Sandé, Friendly Fires and Kelis.
Lovebox Festival takes place between June 15 and June 17 in London's Victoria Park. Tickets, priced between £29.50 and £99, are available now.
> Full Lovebox festival 2012 lineup revealed
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