O2 head of sponsorship Paul Samuels denied the decision was due to declining viewer figures for the last series of 'Big Brother' and said it was time to do something different with the brand. He added that O2 was in discussions with Channel 4 and 'Big Brother' producer Endemol about sponsoring another show.
"'Big Brother' has been a great success for O2 and I am sure it will be for a new sponsor. But we want to try something else that incorporates the same innovation and interactivity," said Samuels.
The sponsorship was a major part of O2's rebrand from BT Cellnet in 2002, and has been credited with raising brand recall among consumers to between 80% and 90%.
It was also hailed across the industry for breaking the mould of traditional programme sponsorships by offering a range of mobile phone and interactive services based on the show.
In the wake of criticism that 'Big Brother' has become stale and the contestants boring, Channel 4 is making changes to the format of the series, and is holding 'Pop Idol'-style open auditions to find more interesting personalities.
The show will also be tougher on contestants, with more arduous challenges.
The mobile firm's three-year sponsorship included one year under the BT Cellnet brand. Southern Comfort sponsored the first series of Big Brother.
The 10-week 'Big Brother 4' series attracted an average audience of 4.5m, 1m down on the previous year.
'Big Brother 5' must now live up to the benchmark set by ITV's 'I'm a Celebrity... Get Me Out of Here!', which this week attracted more than 14m viewers for the final episode of the third series.
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