Entertainment stars Ant and Dec said on Thursday they would return a television comedy award after an investigation found the prize, decided by a viewer telephone vote, should have gone to comedian Catherine Tate.

Singer Robbie Williams presented Ant and Dec - Anthony McPartlin and Declan Donnelly - with the People's Choice Award at ITV's 2005 British Comedy Awards.

But Tate had received more votes and was the correct winner, according to media lawyers Olswang, called in by ITV to investigate the programme.

Olswang said the switch of winner appeared to be connected with an assurance given to Williams that he could present an award to McPartlin and Donnelly.

It noted that the assurance had been given to the former Take That singer at a time when the only prize left to be decided was the People's Choice, selected by a public vote.

Voting was even allowed to continue after the prize had actually been given, when the show was broadcast "as live" following a break for the evening news.

"While it can be concluded that the assurance was given to ensure Robbie Williams' attendance to present an award, it cannot be concluded that this was the reason why the wrong winner of the People's Choice Award was announced," Olswang said.

It added that there was no suggestion that Williams, McPartlin or Donnelly were aware of the switch.

A spokesman for McPartlin and Donnelly said the revelation was "as much a surprise to them as to everybody" and that they would be returning the award.

Publicists for Williams and Tate declined to comment.

ITV published the findings on the same day that media regulator Ofcom fined the broadcaster a record 5.68 million pounds for cheating viewers over phone-in competitions on some of its most popular shows.