Nicholas, who lost out to winner Sam Bailey in Sunday night's finale, criticised his own mentor Louis Walsh for not backing him during the results show.
The 17-year-old from Scotland added that fellow judge Gary Barlow had not supported him throughout the competition.
Louis Walsh and Nicholas McDonald
"I was disappointed with Louis saying, 'Vote for Sam and her single everyone,'" Nicholas told The Daily Mail. "It felt like Sam was getting all the love."
"Gary had a problem with me throughout the whole show," he added. "He never seemed to like me and whenever I gave a good performance he would pick up on the smallest things in the world."
Louis' comment came just after Sam, who has two adorable children, had sung Power of Love.
"Mums all over the country will identify with Sam," said Louis. "I want all of them to vote for Sam Bailey." He then went on to praise the prison officer again, saying that her single would be Christmas number one.
Nicholas and X Factor winner Sam Bailey
Shortly after, Nicholas' family and fans vented their frustration, with the 17-year-old's mother laying in to Louis and Gary.
"It was completely unprofessional, Gary refusing to stand after Nicholas' song," said his mother Eileen.
"As for Louis, I don't know what that was about and it was rude of him. He should have been backing his own act and not encouraging the public to vote for their opponent. I think Louis just speaks without thinking sometimes."
Gary's negative comments came after Nicholas sang Robbie Williams' Candy, which the judge had written himself.
"On a night like tonight it is all about showcasing your strengths and I just didn't think that song showcased your voice," Gary told the singing hopeful. "I think Nicholas is a balladeer at heart and that was going in another area I have never heard you go before."
X Factor bosses confirmed that Nicholas was one of the contestants who did not attend Gary's star-studded after party at The Dorchester hotel.