Successive controversies have seen the number of people taking part in television phone-ins nearly halve, according to a survey.
Research by consultants Oliver & Ohlbaum Associates found that 43 per cent of people who used to participate have now stopped.
Another 20 per cent said they had significantly reduced their involvement, it said.
The survey follows accusations of dishonesty by numerous programmes. This week Ofcom fined GMTV £2 million for allowing people to enter competitions they could not win.
Oliver & Ohlbaum estimated the cut in users meant a drop in income from £400 million to £120 million.
The report added: "Until this summer, participation TV was the golden goose for free-to-air television networks which had seen their traditional advertising revenue come under pressure."
Meanwhile, another report by Mott MacDonald Schema, a management consultancy, showed 89 per cent of former premium rate phone-in users had lost confidence in them.
Well, what did they expect to happen?? I am amazed anyone even bothers to phone in now!! Digital Spy Report