It was Britain's Got Talent act that supposedly "made television history" but some viewers were less impressed with Wendy the "talking dog"– condemning it as a form of animal cruelty.

Broadcasting regulator Ofcom confirmed it has received 30 complaints following ITV's Saturday night (11 April) marvel performance featuring French ventriloquist Marc Metral and his dog Wendy, which brought the house down, including Simon Cowell and the other three judges.

But the act left some people questioning the "cruel" method which was used to give the illusion that the dog's mouth was moving.

The RSPCA told IBTimes UK it would be talking to the award-winning show "to ascertain what methods were used and how they impacted on the dog".

It is likely the dog was wearing some sort of mask over its snout, which was operated remotely by Metral, who has since denied any wrongdoing towards his precious dog.

"I've been working with Wendy since she was a puppy," he told the Daily Star. "I would never put her in a situation that would cause her distress. She gets excited when we go to work and is always comfortable on stage."

An RSPCA spokesman said: "Distress could result from her being unable to breathe or pant properly whilst wearing a mask or muzzle on stage and in an environment which can get very warm, it is essential that panting is not restricted.

"But also, any muzzle or mask should only be used if introduced gradually to the dog and with positive training methods. Dogs should never be forced to wear anything.

"Environments like this have the potential to cause distress to animals in general due to the flashing lights and loud noises and we would hope that Britain's Got Talent has considered very carefully the welfare of any animals being used in performances."

All four judges were bowled over by Metral and Wendy's performance, which included a humourous parody to the song Feelings that saw them through to the next round of the hit show, which attracted a record 11 million viewers.

Afterwards, Cowell was left open-mouthed and said: "Wow, I don't know how she does that. How does she know the words? Unbelievable."

Amanda Holden told Metral: "Congratulations, in the nine years of doing this show, Simon has said he wanted a dog that could meow or sing, and you did both, incredible."

But viewers criticised the act. Abbi Ferguson tweeted: "Totally shocked at BGT putting a mask on an obviously terrified dog; that's not talent. Should be looked into for animal abuse."

A spokesman for BGT said: "Marc has a huge amount of experience having worked with animals since 1980 and with Wendy for the last five years."