"Christina Aguilera is ""up in arms"" over Britney Spears joining ""The X Factor,"" reveals Star. The mag says ""The Voice"" judge is going around bashing her rival, telling people that Spears acts ""like a zombie"" and is ""going to be a disaster"" on the singing competition. For how Spears is striking back at Aguilera's insults, click over to <a target=""_blank"" href=""http://www.gossipcop.com/christina-aguilera-blasts-britney-spears-x-factor-judge-fight-feud/"">Gossip Cop</a>."
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