Television presenters Ant and Dec have confirmed that they will return a comedy award presented to them, after an investigation found that they hadn't actually won the prize.

The award, which was the People's Choice prize, was presented to the TV duo by singer Robbie Williams at the 2005 British Comedy Awards.

An investigation has since concluded that the award, decided by viewers' telephone votes, should have gone to comedy star Catherine Tate.

According to lawyers Olswang, called in by ITV to investigate the programme, Tate had received more votes and was the correct winner of the award.

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

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

Reuters reports that 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.

Olswang said: "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."

It said that there was no suggestion that Williams, McPartlin (Ant) or Donnelly (Dec) were aware of the switch.

A spokesman for Ant and Dec 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 on the story.