Bandmate Max added: "She was a bit scary to be honest."
Siva said: "You know what, she was quite rude."
The boy band also claimed Christina shunned Justin Bieber when he attempted to embrace her.
Nathan said: "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'."
They also claimed they were not allowed to look at Britney Spears while supporting her on tour.
The Glad You Came singers claimed that they were subjected to the diva treatment by the star's team when they were the opening act for her Manchester concert last year.
The group revealed they were not allowed to face her when she exited her venue changing room.
Tom spoke up during an interview on New York radio station Fresh 102.7.
He admitted: "We signed a confidentiality thing that we should never say anything about what happened, but let's tell it anyway."
Siva said: "I was in the hallway with my tour manager. Basically we were looking with a laptop, trying to get WiFi ... facing the middle of the hallway. [Britney's] bouncers came down with her and told us to face the wall."
Tom continued: "As Miss Spears is walking through. We're like, come on!"
Siva added: "We turned around and I faced a wall for about 10 seconds until she got really far away."
-Bang! Showbiz