The Serious Fraud Office is considering an investigation into a string of phone-vote scandals at ITV, including the rigging of an award for Ant and Dec.

The possibility emerged on the day Ofcom warned of "systemic and widespread" problems affecting all broadcasters.

The television watchdog last week handed ITV a record £5.7million fine for abusing premium rate phone services in viewer competitions.

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Ant and Dec with the People's Choice Awards they received in 2006

A separate report released by the channel disclosed that the Catherine Tate Show was robbed of a prize at the 2005 British Comedy Awards.

Although Miss Tate collected more votes from viewers, Ant and Dec's Saturday Night Takeaway was announced as the winner of the People's Choice Award.

Yesterday, Ofcom chief executive Ed Richards told a committee of MPs: "There is, without doubt, a general question about that period which relates to the issue of corporate compliance.

"My view is there is a broader question about the standards of overall corporate compliance in what was clearly systemic and widespread problems."

Questioned over the Ant and Dec scandal, he pointed out that during a previous case concerning GMTV, the Serious Fraud Office had asked to see the files. Mr Richards added: "That may well be what happens again."

Asked by the Culture Select Committee if the fine against ITV would bring the saga to a close, Mr Richards warned that it "certainly isn't the end of the matter" as more cases remain under investigation.

After the Parliamentary committee session, the SFO - an independent government department which investigates serious and complex frauds - confirmed it would be considering the evidence against ITV.

It leaves a cloud hanging over the broadcaster at a time when executives are seeking to repair its battered reputation.

The fine handed down by Ofcom last week was by far the highest ever imposed and was said to reflect the seriousness of ITV's failures and their repeated nature.

Ant and Dec's Saturday Night Takeaway, Gameshow Marathon and Soapstar Superstar were all found to have "serious editorial issues".

Three competitions on Ant and Dec's Saturday Night Takeaway were found to be in breach of the regulators' codes.

Entrants were selected purely based on where they lived, so many callers wasted their money.

On Ant and Dec's Gameshow Marathon, winners were selected based on how entertaining and lively they sounded.

On Soapstar Superstar, producers overrode the viewers' vote, so the wrong participants were put forward for eviction.

ITV made £7.8million from uncounted votes from the programmes involved. The broadcaster has pledged to give the money to charity and to compensate viewers.

In the wake of the scandal over their viewers' award, Anthony McPartlin and Declan Donnelly - better known as Ant and Dec - have promised to return the trophy.

They were given the award because Robbie Williams said he would only appear on the show if it was to hand an award to the two presenters, with whom he is friends.

The singer was completely unaware when he made the agreement that their programme had not won anything, and organisers were relying on them topping the public vote.

But on the night the pair were handed the People's Choice prize - before the public vote had even concluded. It has emerged that Miss Tate should have won.

Last year, the SFO considered investigating GMTV following "deception" in premiumrate phone-in competitions.

A decision was later taken not to proceed.

•The 9pm television watershed is dead, MPs said yesterday.

The division is supposed to protect children from shows which include scenes of violence, sex or swearing.

But MPs on the Culture Select Committee heard it had been rendered obsolete by channels, including the BBC and Channel 4, offering postwatershed programmes throughout the day via their internet sites.

Nigel Evans, the Tory MP for Ribble Valley, said: "The nine o'clock watershed is dead. Anybody who wants to watch anything shown after 9pm can... watch a lot of it on the internet."