An investigation into whether Britain's Got Talent viewers were "misled" by the stunt dog double has been launched by b roadcasting watchdog Ofcom .
The ITV final will be examined after 1,150 complaints poured in about the winning act, Jules O'Dwyer and her dog Matisse.
"We've opened an investigation to determine whether viewers of ITV's Britain's Got Talent final, who may have paid money to vote, were misled about the competition," a spokesman said.
Viewers were outraged after it emerged, on the morning after the final, that Matisse had not performed the tightrope stunt, the most spectacular element of the winning sketch.
It starred O'Dwyer as a policewoman going after "sausage thief" Matisse and another of her pets, three-legged Skippy.
Producers apologised, saying that the use of O'Dwyer's other dog Chase should have been "made clearer to the judges and viewers".
O'Dwyer, who won a spot on the Royal Variety Show as well as the £250,000 prize, said that she was "shocked and surprised" by viewers' reactions.
The guide dog trainer, who beat Welsh choir Cor Glanaethwy and magician Jamie Raven, said she did not use Matisse, the dog which viewers believed performed the stunt, because he did not like heights.
"I was disappointed when people said I allegedly hid Chase and I was trying to make it like Chase was Matisse. That's not so," she said.
"I introduced Chase in the semi-final, and I said Chase is Matisse's best mate. Why put the pressure on the dog when I already have another dog who can perform it on television?"
The show's boss Simon Cowell said "no-one set out to fool anybody" and blamed the "confusion" of a live show for the mix-up.
"I think now the dust has settled a bit we can accept that she won," he said afterwards.
ITV boss Peter Fincham admitted the show should have made it clearer that O'Dwyer used a stunt double dog for her winning sketch.
There was no sign of Chase, who had previously appeared in the semi-final, when O'Dwyer and Matisse took to the stage to be congratulated on their win by the judges and hosts Ant and Dec.
More than 13 million viewers watched O'Dwyer and Matisse become the second dog act to win Britain's Got Talent - following Ashleigh Butler and Pudsey in 2012 - in the highest-rated final since that year.
Voting figures showed that O'Dwyer and Matisse won by just 2% - getting 22.6% of votes compared with 20.4% for magician Raven.
Ofcom will investigate under a rule which states: "Broadcasters must ensure that viewers and listeners are not materially misled about any broadcast competition or voting."