Channel 4 is to scrap most of its profit-making phone-in competitions, following an inquiry into how the contests are run.
Richard and Judy's You Say, We Pay quiz prompted an inquiry
The decision comes after the company behind a quiz on the Richard & Judy show was fined for urging callers to enter after winners had been picked.
Channel 4 executive Anne Bulford said: "Public trust in these competitions has been severely undermined."
Deal or No Deal's contests stay, with a share of profits going to charity.
Eckoh UK Ltd, the company which ran Richard & Judy's You Say, We Pay quiz, was fined £150,000 last month by premium-rate phone services regulator Icstsis.
Following an investigation, Channel 4 discovered problems with the competition dated back to September 2004.
Ms Bulford, who oversaw the inquiry, said: "The investigation has uncovered no evidence that anyone at Channel 4 had any knowledge of or involvement in the improper handling of viewer calls.
"From the moment it came to our attention the channel has done everything possible to protect viewers' interests including having all competitions audited on a live and ongoing basis by appropriate third parties."
Some of Channel 4's most popular programmes will be affected by the decision to scrap the contests, including the daily Paul O'Grady Show.
Competitions are banned from the Paul O'Grady Show
Phone voting for reality TV series Big Brother has continued, but the channel is only charging viewers enough to cover the cost of the call and any charitable donation.
But voting by text message has been banned from all shows, as Channel 4 said it could not be certain of the times and delivery of the messages.
A Channel 4 spokesman said: "As part of the new policy we are getting rid of all competitions we currently do have and we are not introducing any new ones."
Callers who believe they are owed a refund after entering the quiz on the Richard and Judy show have been encouraged to apply for one.
Any remaining profits made from improperly entered calls which are not claimed will be donated to the Great Ormond Street Hospital Children's Charity.
The BBC has suspended all competitions after its own inquiry unearthed a batch of faked phone-in competitions.
The investigation was sparked by the revelation that Blue Peter falsified the results of a phone-in competition during a live show.
And ITV is currently awaiting the results of an external review of its phone-in services following complaints of irregularities in shows including The X Factor.
GMTV bosses have admitted that its quizzes were not run fairly, and are offering refunds to those affected by errors which led entrants ring in for competitions without having any chance of winning.