Tough new rules governing TV quiz shows came into force on Wednesday.

The crackdown by premium rate phone regulator Icstis means that quiz shows will be required to reveal the chances of a caller getting through by displaying on screen the total number of entries received in the preceeding 15 minutes – with the figure updated at least six times per hour.

Some quiz shows have been accused of encouraging viewers to ring in by giving the impression that there are only a few people calling the studio.

Presenters will also have to remind the audience every 10 minutes of the cost of a call, making clear that viewers will be charged regardless of whether or not they are put through to the studio.

And viewers will receive call cost warnings after each £10 spent dialling up a show.

An Icstis spokesman said today: “It is going to be a big step forward in increasing transparency for viewers and boosting viewer confidence. Obviously Icstis will be keeping an eye on programme output and if there are any problems we will act swiftly.”

The new rules apply only to TV quiz shows or channels, and not to general TV shows which include premium rate competitions in their output.