The Prime Minister today warned broadcasters to run television phone-ins in a "reliable and trustworthy way", hours after Michael Grade, ITV's executive chairman, pledged to continue operating the services.

ITV had called in Deloitte, the accountancy firm, this week to conduct an independent audit of the broadcaster's premium rate phone services after viewers were overcharged £200,000 to vote in the last series of The X Factor, while irregularities were discovered at the ITV1 show Ant and Dec's Saturday Night Takeaway.

Speaking at Prime Minister's questions, Mr Blair said that it was a matter of "great concern" to the public, telling MPs: "I totally understand and share the concerns."

He said: “I understand that broadcasters are meeting later this week and I think it is obviously going to be extremely important that the broadcasters come together with the relevant telecommunication companies and make sure that this service is done in a reliable and trustworthy way."

Earlier, an unnamed "whistleblower" from ITV’s quiz operator Eckoh told The Sun that thousands of votes on big-name shows including The X Factor and Who Wants To Be A Millionaire? were being charged at premium rate but not counted because of computer glitches.

She said: "The computers were often going down – you simply wouldn't get through a day without a systems failure.

"Calls still come in thick and fast and viewers are charged at premium rates. But a lot of votes aren't registered. All the big shows are regularly affected."

Undaunted, Mr Grade said this morning that phone-in voting would be restored for Saturday's hit show Dancing on Ice, and that the company remains fully committed to using premium rate services.

The scandal began when it was discovered that viewers were being charged £1 per call to compete in a quiz on Channel 4's Richard & Judy, despite the fact that contestants had already been chosen.

Mr Grade said: "There are concerns about it and there have been mistakes across a number of broadcasters." He added: "We are sure that everything we have on air is compliant but we decided to do a full health check."

As well as examining current premium rate services, John Cresswell, the chief operating officer and finance director at ITV, said that the company will also review premium rate phone-ins over the past two years.

Mr Grade said that audiences enjoyed participating in programmes through phone-in and the rate of 35p to "occasionally" £1 a call was "not expensive".

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