The sponsorship will include Plusnet credits, created by Karmarama, before and after 'Celebrity Big Brother' and its sister show, 'CBB's Bit On The Side', and before and after each ad break.
There will also be Plusnet branding on the show's advertisments, on the 'Celebrity Big Brother' microsite and on short-form content on the official Facebook site, as well as on mobile and iPad.
The sponsorship was negotiated between WPP media agency Maxus and Channel 5.
Nick Rawlings, commercial director at Plusnet, said: "We're delighted to be kicking-off 2012 with such a cracking TV sponsorship, bringing our brand to a whole new audience."
Agostino Di Falco, partnerships director, Channel 5, said: "'Celebrity Big Brother' will reach more young adults than any other programme in January.
"The show kick starts Channel 5's year, and it's great to see Maxus and BT thinking along the same lines in developing this partnership."
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