The former Spice Girl was reportedly booed by the audience after being less than complimentary about an elderly contestant.
Mel is the latest celeb to act as guest judge on the show after Rita Ora, Nicole Scherzinger and her old Spice Girl pal Geri Halliwell made appearances.
But on her first day in the job, Mel felt the wrath of the audience who booed her after she said she ‘wanted to fall asleep’ during 81-year-old widower Lou’s performace.
During the same auditions, Louis Walsh referred to Gary Barlow as Sir Gary after his stint organising the Queen’s Diamond Jubilee concert.
Well, it does have a nice ring to it.