The Masked Singer came under fire after Robobunny was unmasked on tonight's show.
The character was competing on Saturday's Grand Final against Panda and Mushroom.
Robobunny kicked off tonight's showpiece event with a stunning rendition of Run by Snow Patrol.
The second performance was a duet with former winner Nicola Roberts - and the two wowed audiences with their version of Aretha Franklin's I Knew You Were Waiting.
The Girls Aloud singer was convinced she knew the identity of the celebrity behind the extraordinary costume after just four words and said all her "teenage dreams came true" with the performance.
The winners of the show are decided by members of the audience and Robobunny was first to be voted off in tonight's final.
Judges Davina McCall, Mo Gilligan, Jonathan Ross, Rita Ora and Joss Stone made one final guess at who was behind the costume before it was revealed to be Mark Feehily.
However, viewers following the show on Twitter were "horrified" the Westlife legend finished in third place in the competition and felt he was the deserved winner.
Mark said: "Terrible choice Robobunny not being in top 2. Best contestant ever."
Amelia added: "Robobunny was robbed ! Mark is absolutely incredible"
J E Lindsay commented : "I am HORRIFIED that Robobunny hasn't won."
Laura posted: "Markus Feehily elwas robbed!!! Absolutely gutted. You won our hearts Mark!!!"
Lisa tweeted :"How the hell @MarkusFeehily didn't win... The studio audience should never be allowed to vote..."
Jess commented: "you were amazing. Absolutely robbed! You should have won and you would have if it had been a public vote. So many people now know how amazing you are"
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