The former Mis-Teeq singer revealed she reached the end of her tether with her boss after his relentless taunts to her and co-judge Amanda Holden.
Alesha told of how Simon has resorted to making miaowing noises when she and Amanda are delivering negative feedback to female contestants during filming for the new series, which begins on Saturday (15 April).
“This is tradition now, the cat noises,” she said. “There isn’t a day that goes past on the auditions without Simon meowing or making cat noises.
“It’s his own little joke that only he’s in on and only he finds funny. But the most annoying thing about it is you’re trying to concentrate and all you can hear is him meowing.”
She continued: “If I’m in a childish mood then I’ll bite back and start doing something, woofing or something like that, and you suddenly feel like you’re back at school. It’s like we’ve reverted back to being children and I feel so sorry for the producers at that point, they are trying to keep everything calm and it’s really annoying.
“Amanda and I can’t say one thing to a female without him making a meowing noise, it’s so annoying and needs to stop.
“That along with the ‘big fat yes’, they need to go,” she fumed. “If I hear, ‘it’s a big fat yes from me’ one more time, I’m going to scream! Can we try a different type of yes?”
Amanda was in agreement, adding: “Simon is like having a big brother, he’s constantly on mine and Alesha’s back. The minute we say we don’t like a female contestant for one reason or another, he thinks we’re being catty, which is ridiculous.”
The pair have become great pals over the five years they have worked together, and have spoken out in the past about the importance of sticking together as women.
Alesha also said she believes Simon “secretly loves” the fact she and Amanda and really like each other, saying: “He likes that on our show it’s one big dysfunctional, happy family.
“If Amanda and I didn’t have the relationship that we have then it would be a different dynamic, it would be a different show and I might not still be sitting here five or six years later.”
‘Britain’s Got Talent’ launches on Saturday (15 April) at 8pm on ITV.