There has been a "systemic failure" in the way TV channels have run premium rate phone services, Ofcom has found.
Richard and Judy's chat show was the first in a series of phone-in scandals
The media regulator launched an inquiry following a number of scandals involving phone-ins in programmes.
The inquiry found broadcasters were "in denial" about their responsibilities to viewers and saw phone-ins as a way to generate revenue.
The inquiry came on the day the BBC announced it was to suspend all phone-in competitions.
Recent scandals have included the quiz on Channel 4's Richard and Judy chat show, where viewers were still asked to ring in despite a winner already being chosen, and GMTV, which admitted "irregularities" in its phone-in quizzes.
The BBC was recently fined £50,000 by Ofcom for faking the results of a Blue Peter competition in which children had been calling in during the live programme.
The Ofcom inquiry, which was led by Richard Ayre, concluded that broadcasters must be made directly responsible for using premium rate phonelines despite services often being handled by outside companies.
Mr Ayre said: "Phoning a TV show isn't like ordering pizza.
"When you put the phone down nothing arrives: you just have to trust that your call was counted. If broadcasters want audiences to go on spending millions calling in, they need to show they take consumer protection as seriously as programme content."
Ofcom chief executive Ed Richards said: "This inquiry shows the extent to which there has been a systemic failure of compliance.
"Ofcom takes these issues extremely seriously and will continue to take action against broadcasters found to break the rules in this area."