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The Independent Television Commission said the advert for the ITV show left young children "confused and upset".

Dozens of viewers complained about the clip in which the talent show's Mr Nasty appeared to punish the animal for singing badly.

Channel TV, which compiled the promotional clip, said it was "clearly surreal and comical".

The ITC investigated 34 complaints and cleared the advert of encouraging animal cruelty.

But many viewers thought the trailer for the second series of the ITV1 talent show encouraged cruelty to animals even though the tortoise was clearly a puppet.

On one occasion it was screened on directly after The Ark, a show for pre-school children featuring singing animal puppets.

"The ITC felt that the scheduling of the promotion was inappropriate since it was at a time when very young viewers, who would not understand the 'joke', would be viewing," it said.

"Pre-school children often have a very real relationship with puppets and it was clear to the ITC that about a third of the complainants had 3-4-year-olds watching who were confused and upset by the images."