Speaking to New! magazine, she said: “We’re each other’s oldest friends. Our first real successes were with each other, so our journey has always been together.
“He’s truly an honourable, loyal person and he’s fun to be around.
“When you’re in his presence he treats you like you’re the most important person in the room.”
Sinitta is also close with Simon’s partner Lauren Silverman – with whom he has five-year-old son Eric – as she describes her as her “best friend”, and says she’s “very happy” to be so close to the family.
She added: “I’m very happy to be part of that friendship group, though. He trusts me, he knows I have no agenda. It was me who got him on to the diet that led to his weight loss.
“He was starting to look unhealthy and I told him so. He took it on board because it’s me. He’s since told me I saved his life.”
The ‘So Macho hitmaker also dismissed the way the 60-year-old star is seen as ‘Mr Nasty’ thanks to his ruthless judging on his shows – including ‘The X Factor’ and ‘America’s Got Talent’ – and explained he is simply very honest.
She said: “He just says it like he sees it. The other day he was quite rude to me – he was teasing me about fancying [‘The X Factor: Celebrity’ group] Try Star and told me they wouldn’t go for me because I’m too old.
“He said it so bluntly, but that’s just him being matter of fact. I couldn’t really take offence.”