Simon Cowell throws in the towel as BBC wins ratings war

ITV admits defeat in Saturday night duel with The Voice as Britain's Got Talent moves to later slot

Simon Cowell tweeted 'a slightly irritated congrats to Danny and the BBC' after the ratings defeat (AP)

It was as cold and calculated as any of his withering put-downs of wannabe pop stars, and as cynically commercial as his hits you want to hate but can't help singing along to. Yet Simon Cowell's attempt to kill off a rival television show has ended with the kind of defeat that previously only Rage Against the Machine have managed to inflict on the perma-tanned pop impresario.

Having brought Cowell's latest series of Britain's Got Talent forward by several weeks to take viewers away from the BBC's The Voice, ITV has now been forced to push its show back in the Saturday night schedules after losing out in the ratings war.

Episodes of the two talent shows clashed for only 20 minutes, with the beginning of Cowell's franchise starting while Tom Jones and the other stars of The Voice were just reaching their climax on BBC1.

That was enough to cut into the viewing figures for Cowell's show, however. During those crucial 20 minutes, Britain's Got Talent attracted an audience of just 6.2 million, while The Voice held steady with 10 million.

ITV became concerned that this was harming its programme's overall ratings after it garnered 9.1 million viewers on average, compared with 9.5 million for The Voice.

The result is that from 21 April, Britain's Got Talent will be screened at 8.30pm, half an hour later than previously – and 10 minutes after the end of The Voice, which starts at 7pm.

It is perhaps Cowell's biggest miscalculation since, to his great surprise, the heavy-metal band Rage Against the Machine won the 2009 battle against his X Factor singer Joe McElderry for Christmas No 1. He admitted he had lost out in the ratings by tweeting on Sunday: "A slightly irritated congrats to Danny and the BBC," referring to BBC1 controller Danny Cohen.

An unnamed member of the BBC team hinted at the sense of victory within its camp last night. "The BBC always wanted to avoid any overlap but rather than killing The Voice as ITV had hoped, it was instead damaging BGT," they said. "It's no surprise they moved it given last week's ratings."

An ITV spokesman responded by saying its series was proving as successful as ever.

"At its peak, 11.9 million people watched Britain's Got Talent this weekend – the highest recorded audience figure on any channel so far this month," he said. "Viewing figures for BGT are up year on year. By moving to 8.30pm we are ensuring that as many people as possible have the opportunity to watch the show in full."

ITV has insisted that the public-service broadcaster was to blame for the clash. The opening salvo in the ratings war came when the BBC decided to air its show – in which contestants are chosen by the judges on the quality of their voices rather than their image or personality – at the same time of year that ITV has broadcasts theirs since 2008.