Simon was critical towards Andrea and Lauren during Big Band week and now he says that his bad mood was to blame.
The dad-of-one told The Sun: "I had a bad night. I had a really bad headache, I was really grumpy. I want to apologise to Andrea and Lauren because I wasn't being fair."
After Italian singer Andrea performed Ella Fitzgerald's 'Summertime' on Saturday, Simon said it wasn't as good as Leona Lewis' version, and moaned about Andrea's "facial expression".
Meanwhile, Simon was embroiled in a debate with Cheryl Fernandez-Versini about why Lauren didn't move the swing she was sitting on during her performance of Nat King Cole's 'Smile'.
On Sunday, Simon's act Jay James Picton became the latest contestant to be voted off the show, but since then, Simon has hinted that he "would be interested" in offering Jay a record deal.
This weekend's theme will be Elton John vs. Whitney Houston and the remaining acts will once again perform live on stage in the hope of making it through to another week.
On Sunday, performances will come from Take That, Labrinth and David Guetta. Take That's appearance will mark Gary Barlow's return since leaving as a judge last year, and it will also be the first time the group will perform as a three-piece since Jason Orange quit.
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