The judge on the ITV series has claimed that Simon has "very strict rules" about the way women look on his TV shows.
"I have to shape up, wax my legs, up the glamour," Amanda told the Daily Mail. "I’ve been wearing a big dress in Cinderella so I’ve been able to get away with legs as hairy as Gary Lineker’s.
"But Simon Cowell has very strict rules about the way women should look – plucked, waxed, made up and groomed to within an inch of their lives."
Amanda revealed she was fully behind Simon's guidelines, adding: "I agree with him. It’s the Joan Collins method of growing old glamorously."
Meanwhile, Amanda credited Britain's Got Talent and Simon for improving her reputation with the public.
"I had a terrible image before I started BGT and he let people see me as I am. There will always be people who don’t like me but a lot more do now – particularly women. You can only change things one person at a time," Amanda said.
She went on: "The main reason I was so thrilled to stand in for Holly Willoughby during her maternity leave from This Morning [she did a nine-month stint in 2014-15] was that I’d be able to show a different side of myself.
"I wasn’t wearing the big glam frock; I wasn’t judging people. I was talking to people in the news, [covering] a bit of fashion, a bit of cookery, a lot of mums’ issues. I loved every minute. Holly is incredible but if she ever does finally hang up her stilettos, that’s the job I’d really want to be considered for."
Amanda will be back on BGT this Spring on ITV.