The agency will run the brand's press office, while also launching a high-profile brand activation campaign that will include social media activity.
Mischief CEO Mitchell Kaye, who will lead the account, said: ‘The challenge is to play up the iconic heritage of the brand but give people something to talk about in 2012.’
Matt Brown, brand director for United Biscuits, said he had called on Mischief to ‘reignite a passion for Jaffa Cakes’ after the brand had been left without a dedicated PR agency for at least eight years.
He added that he wanted to ‘capture people’s imagination’ and build on the success of a TV advertising campaign last year and the creation of a ‘cult of Jaffa’ website and Facebook community.
He said: ‘We have a fairly large Facebook community, around 320,000 fans, and we wanted to activate their imagination.’
Jaffa Cakes is now the fourth most popular brand in the biscuit market, with three million made per day.