Channel 4 was found guilty, along with its premium rate phoneline operators iTouch and Minick, by Icstis, the regulatory body for premium rate telephone lines in the UK.
The regulator logged 2,635 complaints from members of the public after it was announced that contestants, who had previously been evicted, were being given the chance to return to the house and potentially win the 拢100,000 cash prize.
One contestant who returned to the house after eviction was Nikki, the perfume promotions girl from Middlesex who has since gone on to feature in her own Channel 4 programme 'Princess Nikki'.
Most complainants said they had been misled because they were under the impression they had voted to evict the contestants permanently.
Icstis said its ruling followed a detailed investigation involving Channel 4 and the two premium rate service companies concerned, iTouch, which provided the 090 number telephone voting facility, and Minick, which provided the mobile text vote facility.
In reaching its decision, the regulator said it accepted that 'Big Brother' was an "editorially inventive show", and that the programme's much-publicised statement that 'Big Brother' "reserves the right to change the rules at any time" clearly indicated to viewers that they should expect twists and turns in how the show developed.
However, the regulator said unprecedented number of complaints for this type of service, combined with the undoubted strength of feeling shown by the complainants, clearly indicated that voters genuinely felt that they had been misled in believing that their vote would help permanently evict a member of the house.
Because the 'Big Brother' website stated that "once a housemate leaves they forfeit any claim to the prize money", the regulator concluded that the editorial change had mislead members of the public.
Icstis said that Channel 4 had acknowledged the oversight, but that it had accepted that the intention was not to mislead its viewers. However, the regulator found that paragraph 4.3.1(a) of its code of practice, referring to misleading promotions, had been breached.
The regulator decided not to issue a fine against the broadcaster, because an administration charge to look into the complaint had already been substantial to the two phone operators and Channel 4.
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