Judges' scores are combined with viewer votes to determine which contestant is eliminated each week.
Phillips said she was thrown off by fog on the dance floor during her performance and lost her place.
She said, "I knew that routine. I just blanked."
The Wilson Phillips singer is the fourth contestant eliminated so far on this season of the hit ABC show. Ron Artest (now known as Metta World Peace), Elisabetta Canalis and Kristin Cavallari were ousted on previous episodes
Returning to dance again next week will be Ricki Lake, J.R. Martinez, Chaz Bono, Carson Kressley, David Arquette and Hope Solo.