Carphone Warehouse has sponsored the reality TV show for the past three years, and when the furore surrounding Celebrity Big Brother kicked off, it said it would continue to support the main summer series.
However, Channel 4 is now in talks with other "high-profile" brands for the £2.5 million sponsorship package, which includes branding and advertising opportunities across TV, video-on-demand, online, radio and mobile. The broadcaster hopes to announce a new sponsor within the next eight weeks.
David Charlesworth, the head of sponsorship at Channel 4, said the Big Brother package offered great value for brands. He added: "Big Brother's unpredictability enables it to cut through and build awareness at astonishing speed."