After Jai McDowall, 33, won the Britain's Got Talent in 2011, Simon, 59, said he was "disappointed" but as Jai prepares to make his comeback on Britain's Got Talent: The Champions, Simon admitted he was wrong.
He told The Sun's Bizarre TV column: "I did feel when I saw him again that he's the definition of a proud man.
"He didn't sulk- he just came back to prove a point. And he did.
"I knew I had to apologise to him in that moment. It gave me the chance to say something publicly that I should have said some time ago.
It gave me the chance to say something publicly that I should have said some time ago.
"But it was also the fact that he had the guts to come back and compete, knowing I wasn't supportive the first time he was on the show."
During Jai's comeback episode he receives a standing ovation from Simon and tells the judge: "You have no idea how much that means - thank you.
"Thank you very much, Simon, for everything the show has given me.
"It has given me the lifestyle I can be happy about and the ability to follow my dreams - and I am so thankful for that."
Jai was recruited by producers as a replacement for I Dreamed A Dream singer Susan Boyle - who was runner - up on the show in 2009 and went on to become a huge star - after she was forced to pull out of the special series due to scheduling conflicts.
Susan appeared on America's Got Talent: The champions last year and also released her eighth studio album Ten - celebrating a decade in the spotlight - meaning her schedule is too packed to juggle the show as well.
A spokesperson previously said: "Susan has a busy year ahead with lots of performances coming up, trips to the US, headlining BBC Proms in September, as well as preparing for her upcoming tour.
"She is enjoying celebrating the decade since she first appeared on BGT and her life changing for the better.
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"She loved being part of AGT Champions and wishes the contestants taking part on BGT champions the best of luck."
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