The group criticised the star after meeting her backstage on The Voice USA, where they claim she refused to speak to them.
Max George told 92.3 NOW FM: "She was a bit scary to be honest."
Tom Parker added: "She's a total bitch! She might not be a bitch in real life but to us she was a bitch. She just sat there and didn't speak to us."
Nathan Sykes explained: "She might have been in a bad mood that day - didn't she completely par Justin Bieber as well? He went in for a hug and she was like, 'Get away from me'."
On his recent kiss with Jennifer Lopez on American Idol, George insisted: "J Lo is hot you know, Christina's nothing special."
The Wanted recently revealed that they have the "perfect songs" for their collaborations with Justin Bieber and Chris Brown.
Watch the group discuss Christina Aguilera below: