Ofcom has launched an investigation into the use of premium rate phone lines on television shows as the ongoing controversy over participation TV continues.

ICSTIS, the regulator for premium rate telecom services, is already looking into several instances of alleged irregularities.

An Ofcom inquiry will conduct a wider review of broadcasters, producers and network operators and plans to recommend action to boost viewers' confidence.

Richard Ayre, formerly of BBC News and now a non-executive member of Ofcom's content board, will lead the inquiry and hopes to report by early summer.

Ed Richards, Ofcom's chief executive, said: "Widespread concern about the use of premium rate telephone lines by broadcasters and editorial standards in those programmes has raised serious questions about trust between broadcasters and viewers.

"Ofcom has been monitoring the issue closely and has launched a number of individual investigations since the start of the year. However it is clear from the number of cases underway that a broader set of issues need to be examined as a matter of priority.

"This inquiry will seek to establish the root cause of the compliance issues which have emerged over recent weeks, and inform key decisions about protecting consumers."