The changes have been made after an investigation found that UK callers were paying up to £1.50 a minute to cast votes on closed competitions, which implicated Channel 4's 'Richard & Judy', ITV's 'Dancing on Ice', and the BBC's 'Blue Peter' and 'Saturday Kitchen'.
'Blue Peter' was singled out for intense criticism, after 14,000 children viewers called in to a competition that was won by a member of the studio audience. The BBC said the incident was because of a phone-line fault.
Icstis said the tightened regulations, which have been introduced in its revised Statement of Expectations for Call TV Quiz Services, would "help build consumer trust in quiz TV shows", and respond to concerns raised by MPs in January.
Viewers will now receive clearer real-time information on the likelihood of them getting through to phone-in quizzes, avoiding lengthy and expensive calls that result in little chance of winning.
Additionally, broadcasters will now have to provide permanently visible stand-alone displays that show the total number of quiz entries received, which must be updated every 10 minutes.
More prominent pricing information will also be mandatory, which must be repeated at 10 minute intervals, as will call cost warnings, which tell entrants when they have spent more than £10 a day on phoning a particular quiz.
George Kidd, chief executive of Icstis, said: "We believe these new measures, which are designed to address the concerns that have been raised recently, will go a long way to restoring consumer trust in this form of quiz."
Kidd added that Icstis had been working closely with Ofcom, broadcasters, programme makers and telephone companies, in order to ensure the changes could be made as soon as possible.
In addition to Icstis's new measures, Ofcom is conducting its own investigation into premium rate TV phone-in quizzes. It is understood that the possibility of heavy fines for broadcasters who have fallen foul of the rules has not been ruled out.
Programmes linked to the phone-in scandal, which have all been accused of irregularities and since cleared of any accusations, include BBC One's 'Saturday Kitchen', Channel 4's 'Richard and Judy', and ITV's 'X Factor', 'Dancing on Ice' and 'Ant and Dec's Saturday Night Takeaway'.