Kelly, 18, started the bitter battle with a series of shocking attacks on the 22-year-old DIRRTY singer.
Kelly announced, "She is one of the most disgusting human beings in the world," before going on to describe Christina as looking like a drag queen.
The daughter of shock rocker Ozzy Osbourne then went on to say that Christina is "all talk", before they reportedly came to blows when they bumped into each other at a Hollywood party.
According to the report, Christina ran up to Kelly, put her in a headlock and hissed, "If you've got something to say, say it now! If you ever want to tell me something, tell me in person!"
Their feud - which has yet to be resolved - has landed the pair at number one in the poll by America's IN TOUCH magazine.
The full top 10 is as follows:
1. CHRISTINA AGUILERA + KELLY OSBOURNE
2. Drew Barrymore + JAID BARRYMORE
3. Shannen Doherty + EVERYONE
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